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Abstract Background Human Deltex 2 (DTX2) is a ubiquitin E3 ligase that functions as an oncogene and has been shown to participate in many human cancers. However, the role of DTX2 in glioma progression has remained obscure. In this study, we explore the mechanism underlying the function of DTX2 in glioma progression. Methods The associations between DTX2 expression and clinical characteristics of glioma were determined by bioinformatic analysis of data from The Cancer Genome Atlas and Human Protein Atlas. The expression of DTX2 in glioma tissues was detected using immunohistochemistry and western blotting. Lentivirus-mediated gene knockdown and overexpression were used to determine the effects of DTX2 and helicase-like transcription element (HLTF) on glioma cell proliferation and migration with CCK-8, cell colony formation, transwell, and wound healing assays; flow cytometry in vitro; and animal models in vivo. The interaction of the DTX2 and HLTF proteins was verified by immunoprecipitation assay and confocal microscopy. Results DTX2 was highly expressed in glioma samples, and this was correlated with worse overall survival. Silencing of DTX2 suppressed glioma cell viability, colony formation, and migration and induced cell apoptosis. In vitro ubiquitination assays confirmed that DTX2 could downregulate HLTF protein levels by increasing ubiquitination of the HLTF protein. We also observed that HLTF inhibited proliferation and migration of glioma cells. Subcutaneous xenografts with DTX2-overexpressing U87 cells showed significantly increased tumor volumes and weights. Conclusions We have identified DTX2/HLTF as a new axis in the development of glioma that could serve as a prognostic or therapeutic marker. Graphical abstract

Background: Human Deltex 2 (DTX2) is a ubiquitin E3 ligase that functions as an oncogene and has been shown to participate in many human cancers. However, the role of DTX2 in glioma progression has remained obscure. In this study, we explore the mechanism underlying the function of DTX2 in glioma progression. Methods: The associations between DTX2 expression and clinical characteristics of glioma were determined by bioinformatic analysis of data from The Cancer Genome Atlas and Human Protein Atlas. The expression of DTX2 in glioma tissues was detected using immunohistochemistry and western blotting. Lentivirus-mediated gene knockdown and overexpression were used to determine the effects of DTX2 and helicase-like transcription element (HLTF) on glioma cell proliferation and migration with CCK-8, cell colony formation, transwell, and wound healing assays; flow cytometry in vitro; and animal models in vivo. The interaction of the DTX2 and HLTF proteins was verified by immunoprecipitation assay and confocal microscopy. Results: DTX2 was highly expressed in glioma samples, and this was correlated with worse overall survival. Silencing of DTX2 suppressed glioma cell viability, colony formation, and migration and induced cell apoptosis. In vitro ubiquitination assays confirmed that DTX2 could downregulate HLTF protein levels by increasing ubiquitination of the HLTF protein. We also observed that HLTF inhibited proliferation and migration of glioma cells. Subcutaneous xenografts with DTX2-overexpressing U87 cells showed significantly increased tumor volumes and weights. Conclusions: We have identified DTX2/HLTF as a new axis in the development of glioma that could serve as a prognostic or therapeutic marker. [ABSTRACT FROM AUTHOR]

DNA mismatch repair (MMR) repairs replication errors, and MMR defects play a role in both inherited cancer predisposition syndromes and in sporadic cancers. MMR also recognizes mispairs caused by environmental and chemotherapeutic agents; however, in these cases mispair recognition leads to apoptosis and not repair. Although mutation avoidance by MMR is fairly well understood, MMR-associated proteins are still being identified. We performed a bioinformatic analysis that implicated Saccharomyces cerevisiae Rad5 as a candidate for interacting with the MMR proteins Msh2 and Mlh1. Rad5 is a DNA helicase and E3 ubiquitin ligase involved in post-replicative repair and damage tolerance. We confirmed both interactions and found that the Mlh1 interaction is mediated by a conserved Mlh1-interacting motif (MIP box). Despite this, we did not find a clear role for Rad5 in the canonical MMR mutation avoidance pathway. The interaction of Rad5 with Msh2 and Mlh1 is conserved in humans, although each of the Rad5 human homologs, HLTF and SHPRH, shared only one of the interactions: HLTF interacts with MSH2, and SHPRH interacts with MLH1. Moreover, depletion of SHPRH, but not HLTF, results in a mild increase in resistance to alkylating agents although not as strong as loss of MMR, suggesting gene duplication led to specialization of the MMR-protein associated roles of the human Rad5 homologs. These results provide insights into how MMR accessory factors involved in the MMR-dependent apoptotic response interact with the core MMR machinery and have important health implications into how human cells respond to environmental toxins, tumor development, and treatment choices of tumors with defects in Rad5 homologs.

Retroviruses and their host have coevolved in a delicate balance between viral replication and survival of the infected cell. In this equilibrium, restriction factors expressed by infected cells control different steps of retroviral replication such as entry, uncoating, nuclear import, expression, or budding. Here, we describe a mechanism of restriction against human T cell leukemia virus type 1 (HTLV-1) by the helicase-like transcription factor (HLTF). We show that RNA and protein levels of HLTF are reduced in primary T cells of HTLV-1-infected subjects, suggesting a clinical relevance. We further demonstrate that the viral oncogene Tax represses HLTF transcription via the Enhancer of zeste homolog 2 methyltransferase of the Polycomb repressive complex 2. The Tax protein also directly interacts with HLTF and induces its proteasomal degradation. RNA interference and gene transduction in HTLV-1-infected T cells derived from patients indicate that HLTF is a restriction factor. Restoring the normal levels of HLTF expression induces the dispersal of the Golgi apparatus and overproduction of secretory granules. By synergizing with Tax-mediated NF-κB activation, physiologically relevant levels of HLTF intensify the autophagic flux. Increased vesicular trafficking leads to an enlargement of the lysosomes and the production of large vacuoles containing viral particles. HLTF induction in HTLV-1-infected cells significantly increases the percentage of defective virions. In conclusion, HLTF-mediated activation of the autophagic flux blunts the infectious replication cycle of HTLV-1, revealing an original mode of viral restriction. [ABSTRACT FROM AUTHOR]

Helicase-like transcription factor (HLTF) has been found to be involved in the maintenance of genome stability and tumour suppression, but whether its downregulation in cancers is associated with posttranslational regulation remains unclear. Here, we observed that HLTF was significantly downregulated in hepatocellular carcinoma (HCC) tissues and positively associated with the survival of HCC patients. Mechanistically, the decreased expression of HLTF in HCC was attributed to elevated β-TrCP-mediated ubiquitination and degradation. Knockdown of HLTF enhanced p62 transcriptional activity and mammalian target of rapamycin (mTOR) activation, leading to HCC tumourigenesis. Inhibition of mTOR effectively blocked β-TrCP overexpression- or HLTF knockdown-mediated HCC tumourigenesis and metastasis. Furthermore, in clinical tissues, decreased HLTF expression was positively correlated with elevated expression of β-TrCP, p62, or p-mTOR in HCC patients. Overall, our data not only uncover new roles of HLTF in HCC cell proliferation and metastasis, but also reveal a novel posttranslational modification of HLTF by β-TrCP, indicating that the β-TrCP/HLTF/p62/mTOR axis may be a new oncogenic driver involved in HCC development. This finding provides a potential therapeutic strategy for HCC patients by targeting the β-TrCP/HLTF/p62/mTOR axis. [ABSTRACT FROM AUTHOR]

Objectives: Cervical carcinoma (CC) is prevalent among women worldwide with increasing risk. Finding effective methods for treating CC is of utmost importance. The aim of this study was to investigate the effect of SERPINE1 on the progression of cervical precancerous lesions to CC., Design: This study used transcriptome sequencing and in vitro cell line. Participants/Materials: Cervical precancerous lesions and CC samples and human cervical epithelial immortalized cell line H8, human CC cell lines HeLa, and CaSki were involved in this study., Setting and Methods: Next-generation sequencing was applied to identify 100 differentially expressed genes from cervical precancerous lesions and CC samples. With the application of the Search Tool for the Retrieval of Interacting Genes (STRING) database, we carried out the protein-protein interaction network analysis, thus screening out serine protease inhibitor clade E member 1 (SERPINE1) with significant upregulation in CC cells. The helicase-like transcription factor (HLTF) was predicted as the upstream transcription factor using Human Transcription Factor Database (HumanTFDB). The chromatin immunoprecipitation (ChIP) experiment was conducted to validate the interaction between SERPINE1 and HLTF. The immunohistochemistry was employed to determine the expression of SERPINE1 and HLTF in CC tissues. Following the upregulation or downregulation of SERPINE1 and HLTF, the real-time quantitative reverse transcription polymerase chain reaction was carried out to assess mRNA expression levels of SERPINE1 and HLTF in cells. Cell viability, migration, and invasion were evaluated using MTT assay, cell scratch assay, and Transwell assay, respectively. Western blot analysis was conducted to assess changes in the expression levels of matrix metalloproteinases and proteins related to epithelial-mesenchymal transition (EMT)., Results: The ChIP experiment confirmed the interaction between HLTF and SERPINE1. HLTF and SERPINE1 were upregulated in CC tissues and cells, and silencing SERPINE1 inhibited the EMT process and viability, migration, and invasion of CC cells. However, overexpression of SERPINE1 in CC cells showed the opposite trend. Rescue experiments demonstrated that silencing HLTF repressed CC cell viability, migration, and invasion, which could be restored by overexpressing SERPINE1., Limitations: The effect of the HLTF/SERPINE1 axis on CC malignant progression has not been confirmed by in vivo experiments., Conclusion: HLTF transcriptionally activates SERPINE1, promoting the progression from cervical precancerous lesions to CC., (© 2024 S. Karger AG, Basel.)

Stalled replication forks need to be swiftly detected and protected from collapse and the cause for fork stall be removed to restore the active replication fork. In bacteria, stalled forks are recognized and stabilized by PriA, a DEXH-type helicase, which also facilitates reassembly of an active replication fork. A TT-pocket (three-prime terminus binding pocket) present in the N-terminal segment of PriA plays a crucial role in stabilization of the stalled forks by specifically binding to the 3 |$^\prime$| -terminus of the nascent leading strand. Eukaryotic proteins, Rad5/HLTF, contain a TT-pocket related domain, HIRAN, that specifically binds to 3′-terminus of DNA and play a role in stalled fork processing. While the TT-pocket of PriA facilitates the formation of an apparently stable and immobile complex on a fork with a 3′-terminus at the fork junction, HIRAN of Rad5/HLTF facilitates fork regression by itself. A recent report shows that HIRAN can displace 3 nucleotides at the end of the duplex DNA, providing mechanistic insight into how stalled forks are reversed in eukaryotes. In this article, I will compare the roles of 3′-terminus binding domains in stalled fork processing in prokaryotes and in eukaryotes. [ABSTRACT FROM AUTHOR]

DNA mismatch repair (MMR) repairs replication errors, and MMR defects play a role in both inherited cancer predisposition syndromes and in sporadic cancers. MMR also recognizes mispairs caused by environmental and chemotherapeutic agents; however, in these cases mispair recognition leads to apoptosis and not repair. Although mutation avoidance by MMR is fairly well understood, MMR-associated proteins are still being identified. We performed a bioinformatic analysis that implicated Saccharomyces cerevisiae Rad5 as a candidate for interacting with the MMR proteins Msh2 and Mlh1. Rad5 is a DNA helicase and E3 ubiquitin ligase involved in post-replicative repair and damage tolerance. We confirmed both interactions and found that the Mlh1 interaction is mediated by a conserved Mlh1-interacting motif (MIP box). Despite this, we did not find a clear role for Rad5 in the canonical MMR mutation avoidance pathway. The interaction of Rad5 with Msh2 and Mlh1 is conserved in humans, although each of the Rad5 human homologs, HLTF and SHPRH, shared only one of the interactions: HLTF interacts with MSH2, and SHPRH interacts with MLH1. Moreover, depletion of SHPRH, but not HLTF, results in a mild increase in resistance to alkylating agents although not as strong as loss of MMR, suggesting gene duplication led to specialization of the MMR-protein associated roles of the human Rad5 homologs. These results provide insights into how MMR accessory factors involved in the MMR-dependent apoptotic response interact with the core MMR machinery and have important health implications into how human cells respond to environmental toxins, tumor development, and treatment choices of tumors with defects in Rad5 homologs.

Background and Objective: Colorectal Cancer (CRC) is the third most common cancer after prostate (breast in women) and lung cancer; it is also the third cause of cancer deaths reported in both men and women in 2020. Currently, the most commonly used diagnostic tools for CRC are colonoscopy, serological methods, and other imaging techniques. Despite the benefits and abilities of these methods, each of them has disadvantages that reduce its functionality and acceptance. The aim of this study was identifying specific and non-invasive genetic biomarkers to diagnose colorectal cancer. Methods & Material: In this study, changes in the expression of HLTF and SEPT9 genes were evaluated by Real Time PCR in blood and tissue samples of CRC patients. A total of 100 samples (50 Blood and 50 Tissue samples) were evaluated with a definite diagnosis of CRC in Firoozgar Hspital, Tehran, Iran, in 2018. The QPCR method was used to compare the expression of candidate genes between the patients group and control group in both samples. Sensitivity and specificity of the test were examined using ROC curve analysis. Results: The results showed a significant down-regulation in the expression of both selected genes in tissue and peripheral blood in the various stages of the CRC. The sensitivity and specifity of both genes was about 80%. Conclusion: The findings showed that the two candidate genes can be suggested as specific biomarkers for diagnosis of CRC using the peripheral blood as a non-invasive method. For a definite conclusion, more research is needed.

G-quadruplexes (G4s) form throughout the genome and influence important cellular processes. Their deregulation can challenge DNA replication fork progression and threaten genome stability. Here, we demonstrate an unexpected role for the double-stranded DNA (dsDNA) translocase helicase-like transcription factor (HLTF) in responding to G4s. We show that HLTF, which is enriched at G4s in the human genome, can directly unfold G4s in vitro and uses this ATP-dependent translocase function to suppress G4 accumulation throughout the cell cycle. Additionally, MSH2 (a component of MutS heterodimers that bind G4s) and HLTF act synergistically to suppress G4 accumulation, restrict alternative lengthening of telomeres, and promote resistance to G4-stabilizing drugs. In a discrete but complementary role, HLTF restrains DNA synthesis when G4s are stabilized by suppressing primase-polymerase (PrimPol)-dependent repriming. Together, the distinct roles of HLTF in the G4 response prevent DNA damage and potentially mutagenic replication to safeguard genome stability. [Display omitted] • HLTF is enriched at G4s and suppresses G4 accumulation in all cell cycle phases • HLTF translocase directly resolves G4 structures using its ATPase activity • HLTF restrains DNA synthesis and suppresses PrimPol in response to G4 stabilization • HLTF protects cells from DNA damage and growth defects induced by G4 stabilization Bai et al. identify an unexpected function for the helicase-like transcription factor, HLTF, in suppressing G-quadruplexes (G4s), a DNA secondary structure that can threaten genome stability. HLTF uses its DNA translocase activity to unfold G4s in dsDNA and to restore the DNA duplex, and it restrains DNA synthesis at G4s. [ABSTRACT FROM AUTHOR]

The Rad5 family of proteins are critical genome maintenance factors, with helicase-like transcription factor (HLTF) and SNF2 histone linker PHD RING helicase (SHRPH) in humans implicated in several types of cancer. How their multiple activities coordinate has been unclear. Our recent study on Rad5 shed light on this question.

DNA replication is laden with obstacles that slow, stall, collapse, and break DNA replication forks. At each obstacle, there is a decision to be made whether to bypass the lesion, repair or restart the damaged fork, or to protect stalled forks from further demise. Each "decision" draws upon multitude of proteins participating in various mechanisms that allow repair and restart of replication forks. Specific functions for many of these proteins have been described and an understanding of how they come together in supporting replication forks is starting to emerge. Many questions, however, remain regarding selection of the mechanisms that enable faithful genome duplication and how "normal" intermediates in these mechanisms are sometimes funneled into "rogue" processes that destabilize the genome and lead to cancer, cell death, and emergence of chemotherapeutic resistance. In this review we will discuss molecular mechanisms of DNA damage bypass and replication fork protection and repair. We will specifically focus on the key players that define which mechanism is employed including: PCNA and its control by posttranslational modifications, translesion synthesis DNA polymerases, molecular motors that catalyze reversal of stalled replication forks, proteins that antagonize fork reversal and protect reversed forks from nucleolytic degradation, and the machinery of homologous recombination that helps to reestablish broken forks. We will also discuss risks to genome integrity inherent in each of these mechanisms. [ABSTRACT FROM AUTHOR]

Background & Objective: olorectal Cancer (CRC) is the third most common cancer after prostate (breast in women) and lung cancer; it is also the third cause of cancer deaths reported in both men and women in 2020. Currently, the most commonly used diagnostic tools for CRC are colonoscopy, serological methods, and other imaging techniques. Despite the benefits and abilities of these methods, each of them has disadvantages that reduce its functionality and acceptance. The aim of this study was identifying specific and non-invasive genetic biomarkers to diagnose colorectal cancer. Methods: In this study, changes in the expression of HLTF and SEPT9 genes were evaluated by Real Time PCR in blood and tissue samples of CRC patients. A total of 100 samples (50 Blood and 50 Tissue samples) were evaluated with a definite diagnosis of CRC in Firoozgar Hspital, Tehran, Iran, in 2018. The QPCR method was used to compare the expression of candidate genes between the patients group and control group in both samples. Sensitivity and specificity of the test were examined using ROC curve analysis. Results: The results showed a significant down-regulation in the expression of both selected genes in tissue and peripheral blood in the various stages of the CRC. The sensitivity and specifity of both genes was about 80%. Conclusion: The findings showed that the two candidate genes can be suggested as specific biomarkers for diagnosis of CRC using the peripheral blood as a noninvasive method. For a definite conclusion, more research is needed. [ABSTRACT FROM AUTHOR]

Abstract Background The relapse rate in early stage non-small cell lung cancer (NSCLC) after surgical resection is high. Prognostic biomarkers may help identify patients who may benefit from additional therapy. The Helicase-like Transcription Factor (HLTF) is a tumor suppressor, altered in cancer either by gene hypermethylation or mRNA alternative splicing. This study assessed the expression and the clinical relevance of wild-type (WT) and variant forms of HLTF RNAs in NSCLC. Methods We analyzed online databases (TCGA, COSMIC) for HLTF alterations in NSCLC and assessed WT and spliced HLTF mRNAs expression by RT-ddPCR in 39 lung cancer cell lines and 171 patients with resected stage I-II NSCLC. Results In silico analyses identified HLTF gene alterations more frequently in lung squamous cell carcinoma than in adenocarcinoma. In cell lines and in patients, WT and I21R HLTF mRNAs were detected, but the latter at lower level. The subgroup of 25 patients presenting a combined low WT HLTF expression and a high I21R HLTF expression had a significantly worse disease-free survival than the other 146 patients in univariate (HR 1.96, CI 1.17–3.30; p = 0.011) and multivariate analyses (HR 1.98, CI 1.15–3.40; p = 0.014). Conclusion A low WT HLTF expression with a high I21R HLTF expression is associated with a poor DFS.

The eukaryotic post-replication repair (PRR) pathway allows completion of DNA replication when replication forks encounter lesions on the DNA template and are mediated by post-translational ubiquitination of the DNA sliding clamp proliferating cell nuclear antigen (PCNA). Monoubiquitinated PCNA recruits translesion synthesis (TLS) polymerases to replicate past DNA lesions in an error-prone manner while addition of K63-linked polyubiquitin chains signals for error-free template switching to the sister chromatid. Central to both branches is the E3 ubiquitin ligase and DNA helicase Rad5/helicase-like transcription factor (HLTF). Mutations in PRR pathway components lead to genomic rearrangements, cancer predisposition, and cancer progression. Recent studies have challenged the notion that the PRR pathway is involved only in DNA lesion tolerance and have shed new light on its roles in cancer progression. Molecular details of Rad5/HLTF recruitment and function at replication forks have emerged. Mounting evidence indicates that PRR is required during lesion-less replication stress, leading to TLS polymerase activity on undamaged templates. Analysis of PRR mutation status in human cancers and PRR function in cancer models indicates that down regulation of PRR activity is a viable strategy to inhibit cancer cell growth and reduce chemoresistance. Here, we review these findings, discuss how they change our views of current PRR models, and look forward to targeting the PRR pathway in the clinic. [ABSTRACT FROM AUTHOR]

Lentiviruses, including HIV-1, possess the ability to enter the nucleus through nuclear pore complexes and can infect interphase cells, including those actively replicating chromosomal DNA. Viral accessory proteins hijack host cell E3 enzymes to antagonize intrinsic defenses, and thereby provide a more permissive environment for virus replication. The HIV-1 Vpr accessory protein reprograms CRL4DCAF1 E3 to antagonize select postreplication DNA repair enzymes and activates the DNA damage checkpoint in the G2 cell cycle phase. However, little is known about the roles played by these Vpr targets in HIV-1 replication. Here, using a sensitive pairwise replication competition assay, we show that Vpr endows HIV-1 with a strong replication advantage in activated primary CD4+ T cells and established T cell lines. This effect is disabled by a Vpr mutation that abolishes binding to CRL4DCAF1 E3, thereby disrupting Vpr antagonism of helicase-like transcription factor (HLTF) DNA helicase and other DNA repair pathway targets, and by another mutation that prevents induction of the G2 DNA damage checkpoint. Consistent with these findings, we also show that HLTF restricts HIV-1 replication, and that this restriction is antagonized by HIV-1 Vpr. Furthermore, our data imply that HIV-1 Vpr uses additional, yet to be identified mechanisms to facilitate HIV-1 replication in T cells. Overall, we demonstrate that multiple aspects of the cellular DNA repair machinery restrict HIV-1 replication in dividing T cells, the primary target of HIV-1 infection, and describe newly developed approaches to dissect key components. [ABSTRACT FROM AUTHOR]

The Rad5 family of proteins are critical genome maintenance factors, with helicase-like transcription factor (HLTF) and SNF2 histone linker PHD RING helicase (SHRPH) in humans implicated in several types of cancer. How their multiple activities coordinate has been unclear. Our recent study on Rad5 shed light on this question. [ABSTRACT FROM AUTHOR]

Not only have helicase-like transcription factor (HLTF) and SNF2 histone-linker PHD-finger RING-finger helicase (SHPRH) proved to be important players in post-replication repair like their yeast counterpart, Rad5, but they are also involved in multiple biological functions and are associated with several human disorders. We provide here an updated view of their functions, associated diseases, and potential therapeutic approaches. [ABSTRACT FROM AUTHOR]

Background: The relapse rate in early stage non-small cell lung cancer (NSCLC) after surgical resection is high. Prognostic biomarkers may help identify patients who may benefit from additional therapy. The Helicase-like Transcription Factor (HLTF) is a tumor suppressor, altered in cancer either by gene hypermethylation or mRNA alternative splicing. This study assessed the expression and the clinical relevance of wild-type (WT) and variant forms of HLTF RNAs in NSCLC.Methods: We analyzed online databases (TCGA, COSMIC) for HLTF alterations in NSCLC and assessed WT and spliced HLTF mRNAs expression by RT-ddPCR in 39 lung cancer cell lines and 171 patients with resected stage I-II NSCLC.Results: In silico analyses identified HLTF gene alterations more frequently in lung squamous cell carcinoma than in adenocarcinoma. In cell lines and in patients, WT and I21R HLTF mRNAs were detected, but the latter at lower level. The subgroup of 25 patients presenting a combined low WT HLTF expression and a high I21R HLTF expression had a significantly worse disease-free survival than the other 146 patients in univariate (HR 1.96, CI 1.17-3.30; p = 0.011) and multivariate analyses (HR 1.98, CI 1.15-3.40; p = 0.014).Conclusion: A low WT HLTF expression with a high I21R HLTF expression is associated with a poor DFS. [ABSTRACT FROM AUTHOR]

Lysosomal autophagy inhibitors (LAI) such as hydroxychloroquine (HCQ) have significant activity in a subset of cancer cell lines. LAIs are being evaluated in cancer clinical trials, but genetic determinants of sensitivity to LAIs are unknown, making it difficult to predict which tumors would be most susceptible. Here we characterize differentially expressed genes in HCQ-sensitive (-S) and -resistant (-R) cancer cells. Notably, expression of canonical macroautophagy/autophagy genes was not associated with sensitivity to HCQ. Expression patterns of ALDH1A1 (aldehyde dehydrogenase 1 family member A1) and HLTF (helicase like transcription factor) identified HCQ-S (ALDH1A1highHLTFlow; ALDH1A1lowHLTFlow) and HCQ-R (ALDH1A1lowHLTFhigh) cells. ALDH1A1 overexpression was found to enhance LAI cell entry and cytotoxicity without directly affecting lysosome function or autophagic flux. Expression of HLTF allows repair of DNA damage caused by LAI-induced reactive oxygen species, leading to HCQ resistance. Sensitivity to HCQ is increased in cells whereHLTFis silenced by promoter methylation. HLTF overexpression blunted the antitumor efficacy of chloroquine derivatives in vitro and in vivo. Analysis of tumor RNA sequencing data from >700 patients in the Cancer Genome Atlas identified cancers including colon cancer, renal cell carcinoma, and gastric cancers, that were enriched for the HCQ-S or HCQ-R signature. These results provide mechanistic insights into LAI efficacy, and guidance for LAI clinical development. [ABSTRACT FROM PUBLISHER]

The arginine dependency of cancer cells creates metabolic vulnerability. In this study, we examine the impact of arginine availability on DNA replication and genotoxicity resistance. Using DNA combing assays, we find that limiting extracellular arginine results in the arrest of cancer cells at S phase and a slowing or stalling of DNA replication. The translation of new histone H4 is arginine dependent and influences DNA replication. Increased proliferating cell nuclear antigen (PCNA) occupancy and helicase-like transcription factor (HLTF)-catalyzed PCNA K63-linked polyubiquitination protect arginine-starved cells from DNA damage. Arginine-deprived cancer cells display tolerance to genotoxicity in a PCNA K63-linked polyubiquitination-dependent manner. Our findings highlight the crucial role of extracellular arginine in nutrient-regulated DNA replication and provide potential avenues for the development of cancer treatments. [Display omitted] • Arginine shortage halts H4 histone synthesis, stalling DNA replication • Fork stalling creates vulnerability of nascent DNA strands to DNA2-mediated degradation • Cells respond to arginine deprivation by HLTF-mediated K63-polyubiquitination of PCNA • HLTF and PCNA polyubiquitylation protect arginine-starved cells from DNA damage agents Wang et al. find that arginine shortage can temporarily place DNA replication on hold via inhibiting histone H4 translation and stalling fork movement. They show that this is associated with HLTF-mediated K63-linked polyubiquitination of PCNA, which increases PCNA's presence on nascent DNA strands, and helps cells tolerate DNA damage. [ABSTRACT FROM AUTHOR]

HLTF is a SWI2/SNF2-family ATP-dependent chromatin remodeling enzyme that acts in the error-free branch of DNA damage tolerance (DDT), a cellular mechanism that enables replication of damaged DNA while leaving damage repair for a later time. Human HLTF and a closely related protein SHPRH, as well as their yeast homologue Rad5, are multi-functional enzymes that share E3 ubiquitin-ligase activity required for activation of the error-free DDT. HLTF and Rad5 also function as ATP-dependent dsDNA translocases and possess replication fork reversal activities. Thus, they can convert Y-shaped replication forks into X-shaped Holliday junction structures that allow error-free replication over DNA lesions. The fork reversal activity of HLTF is dependent on 3′-ssDNA-end binding activity of its N-terminal HIRAN domain. Here we present the solution NMR structure of the human HLTF HIRAN domain, an OB-like fold module found in organisms from bacteria (as a stand-alone domain) to plants, fungi and metazoan (in combination with SWI2/SNF2 helicase-like domain). The obtained structure of free HLTF HIRAN is similar to recently reported structures of its DNA bound form, while the NMR analysis also reveals that the DNA binding site of the free domain exhibits conformational heterogeneity. Sequence comparison of N-terminal regions of HLTF, SHPRH and Rad5 aided by knowledge of the HLTF HIRAN structure suggests that the SHPRH N-terminus also includes an uncharacterized structured module, exhibiting weak sequence similarity with HIRAN regions of HLTF and Rad5, and potentially playing a similar functional role. [ABSTRACT FROM AUTHOR]

The Helicase-like Transcription Factor (HLTF) belongs to the SWI/SNF family of proteins involved in chromatin remodeling. In addition to its role in gene transcription, HLTF has been implicated in DNA repair, which suggests that this protein acts as a tumor suppressor. Accumulating evidence indicates that HLTF expression is altered in various cancers via two mechanisms: gene silencing through promoter hypermethylation or alternative mRNA splicing, which leads to the expression of truncated proteins that lack DNA repair domains. In either case, the alteration of HLTF expression in cancer has a poor prognosis. In this review, we gathered published clinical and molecular data on HLTF. Our purposes are (a) to address whether HLTF alterations could be considered as cancer drivers or passengers and (b) to determine whether its different functions (transcription or DNA repair) could be diverted in clonal selection during cancer progression. [ABSTRACT FROM AUTHOR]

Background: The preoperative characterization of thyroid nodules is a challenge for the clinicians. Fine-needle aspiration (FNA) is the commonly used pre-operative technique for diagnosis of malignant thyroid tumor. However, many benign lesions, with indeterminate diagnosis following FNA, are referred to surgery. There is an urgent need to identify biomarkers that could be used with the FNA to distinguish benign thyroid nodules from malignant tumors. The purpose of the study is to examine the level of expression of the helicase-like transcription factor (HLTF) in relation to neoplastic progression of thyroid carcinomas. Methods: The presence of HLTF was investigated using quantitative and semi-quantitative immunohistochemistry in a series of 149 thyroid lesion specimens. Our first clinical series was composed of 80 patients, including 20 patients presenting thyroid adenoma, 40 patients presenting thyroid papillary carcinoma, 12 patients presenting thyroid follicular carcinoma and 8 patients presenting anaplastic carcinoma. These specimens were assessed quantitatively using computer assisted microscopy. Our initial results were validated on a second clinical series composed of 40 benign thyroid lesions and 29 malignant thyroid lesions using a semi-quantitative approach. Finally, the HLTF protein expression was investigated by Western blotting in four thyroid cancer cell lines. Results: The decrease of HLTF staining was statistically significant during thyroid tumor progression in terms of both the percentage of mean optical density (MOD), which corresponds to the mean staining intensity (Kruskall-Wallis: p < 0.0005), and the labelling index (LI), which corresponds to the percentage of immunopositive cells (Kruskall-Wallis: p < 10-6). Adenomas presented very pronounced nuclear HLTF immunostaining, whereas papillary carcinomas exhibited HLTF only in the cytoplasm. The number of HLTF positive nuclei was clearly higher in the adenomas group (30%) than in the papillary carcinomas group (5%). The 115-kDa full size HLTF protein was immunodetected in four studied thyroid cancer cell lines. Moreover, three truncated HLTF forms (95-kDa, 80-kDa and 70-kDa) were also found in these tumor cells. Conclusions: This study reveals an association between HLTF expression level and thyroid neoplastic progression. Nuclear HLTF immunostaining could be used with FNA in an attempt to better distinguish benign thyroid nodules from malignant tumors. [ABSTRACT FROM AUTHOR]

Background: Hypermethylation of DNA is an epigenetic alteration commonly found in colorectal cancer (CRC) and can also be detected in blood samples of cancer patients. Methylation of the genes helicase-like transcription factor (HLTF) and hyperplastic polyposis 1 (HPP1) have been proposed as prognostic, and neurogenin 1 (NEUROG1) as diagnostic biomarker. However the underlying mechanisms leading to the release of these genes are unclear. This study aimed at examining the possible correlation of the presence of methylated genes NEUROG1, HLTF and HPP1 in serum with tissue breakdown as a possible mechanism using serum lactate dehydrogenase (LDH) as a surrogate marker. Additionally the prognostic impact of these markers was examined. Methods: Pretherapeutic serum samples from 259 patients from all cancer stages were analyzed. Presence of hypermethylation of the genes HLTF, HPP1, and NEUROG1 was examined using methylation-specific quantitative PCR (MethyLight). LDH was determined using an UV kinetic test. Results: Hypermethylation of HLTF and HPP1 was detected significantly more often in patients with elevated LDH levels (32% vs. 12% [p = 0.0005], and 68% vs. 11% [p < 0.0001], respectively). Also, higher LDH values correlated with a higher percentage of a fully methylated reference in a linear fashion (Spearman correlation coefficient 0.18 for HLTF [p = 0.004]; 0.49 [p < .0001] for HPP1). No correlation between methylation of NEUROG1 and LDH was found in this study. Concerning the clinical characteristics, high levels of LDH as well as methylation of HLTF and HPP1 were significantly associated with larger and more advanced stages of CRC. Accordingly, these three markers were correlated with significantly shorter survival in the overall population. Moreover, all three identified patients with a worse prognosis in the subgroup of stage IV patients. Conclusions: We were able to provide evidence that methylation of HLTF and especially HPP1 detected in serum is strongly correlated with cell death in CRC using LDH as surrogate marker. Additionally, we found that prognostic information is given by both HLTF and HPP1 as well as LDH. In sum, determining the methylation of HLTF and HPP1 in serum might be useful in order to identify patients with more aggressive tumors. [ABSTRACT FROM AUTHOR]

Nucleotide excision repair (NER) counteracts the onset of cancer and aging by removing helix-distorting DNA lesions via a "cut-and-patch"-type reaction. The regulatory mechanisms that drive NER through its successive damage recognition, verification, incision, and gap restoration reaction steps remain elusive. Here, we show that the RAD5-related translocase HLTF facilitates repair through active eviction of incised damaged DNA together with associated repair proteins. Our data show a dual-incision-dependent recruitment of HLTF to the NER incision complex, which is mediated by HLTF's HIRAN domain that binds 3′-OH single-stranded DNA ends. HLTF's translocase motor subsequently promotes the dissociation of the stably damage-bound incision complex together with the incised oligonucleotide, allowing for an efficient PCNA loading and initiation of repair synthesis. Our findings uncover HLTF as an important NER factor that actively evicts DNA damage, thereby providing additional quality control by coordinating the transition between the excision and DNA synthesis steps to safeguard genome integrity. [Display omitted] • HLTF stimulates NER independent from PRR • HIRAN-dependent HLTF is recruited to NER sites upon dual incision by XPF-ERCC1 and XPG • HLTF's ATPase domain evicts the damage-containing incision fragment • HLTF-mediated damage removal is required for efficient repair synthesis van Toorn et al. report that HLTF, mainly known for its role in post-replication repair, is required for efficient nucleotide excision repair. HLTF is recruited after dual incision to actively evict damage-containing oligonucleotides and facilitate repair synthesis. [ABSTRACT FROM AUTHOR]

DNA mismatch repair (MMR) repairs replication errors, and MMR defects play a role in both inherited cancer predisposition syndromes and in sporadic cancers. MMR also recognizes mispairs caused by environmental and chemotherapeutic agents; however, in these cases mispair recognition leads to apoptosis and not repair. Although mutation avoidance by MMR is fairly well understood, MMR-associated proteins are still being identified. We performed a bioinformatic analysis that implicated Saccharomyces cerevisiae Rad5 as a candidate for interacting with the MMR proteins Msh2 and Mlh1. Rad5 is a DNA helicase and E3 ubiquitin ligase involved in post-replicative repair and damage tolerance. We confirmed both interactions and found that the Mlh1 interaction is mediated by a conserved Mlh1-interacting motif (MIP box). Despite this, we did not find a clear role for Rad5 in the canonical MMR mutation avoidance pathway. The interaction of Rad5 with Msh2 and Mlh1 is conserved in humans, although each of the Rad5 human homologs, HLTF and SHPRH, shared only one of the interactions: HLTF interacts with MSH2, and SHPRH interacts with MLH1. Moreover, depletion of SHPRH, but not HLTF, results in a mild increase in resistance to alkylating agents although not as strong as loss of MMR, suggesting gene duplication led to specialization of the MMR-protein associated roles of the human Rad5 homologs. These results provide insights into how MMR accessory factors involved in the MMR-dependent apoptotic response interact with the core MMR machinery and have important health implications into how human cells respond to environmental toxins, tumor development, and treatment choices of tumors with defects in Rad5 homologs., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Miller, Mao, Knicely, Daniels, Rahal, Putnam, Kolodner and Goellner.)

DNA hypermethylation is frequently found in colorectal cancer (CRC). Methylation of helicase-like transcription factor (HLTF) and hyperplastic polyposis 1 (HPP1) are potential and carcinoembryonic antigen (CEA) is an established prognostic factor in serum of patients with CRC. The aim of this study was to perform a direct comparison of the prognostic roles of these markers. Methylation status of HLTF and HPP1 was examined in pretherapeutic sera of 311 patients with CRC and matched primary tissues of 54 stage IV patients using methylation-specific quantitative PCR. CEA was determined using an immunoenzymometric assay. Methylation of HLTF and HPP1 DNA in serum significantly correlated with tumor size, stage, grade and metastatic disease. HPP1 methylation correlated with nodal status. Overall survival was shortened in case of methylation of HLTF or HPP1 or elevated levels of CEA ( p < 0.0001 for all). In stage IV, patients survival was impaired if HLTF ( p = 0.0005) or HPP1 ( p = 0.0003) were methylated or CEA was above the median of 27 ng/ml ( p = 0.002). Multivariate analysis revealed that methylation of HLTF [hazard ratio (HR) 1.8, p = 0.0438], HPP1 (HR 1.6, p = 0.0495) and CEA >27 ng/ml (HR 1.7, p = 0.0317) were independent prognostic factors in stage IV. The combination of any two or all three of these factors outperformed each marker on its own. In conclusion, the presence of methylated DNA of the genes HLTF or HPP1 in serum are independent prognostic factors in metastasized CRC. Prospective validation is required to determine their usefulness in clinical routine along with the established marker CEA. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To investigate the promoter methylation of HLTF in the tissues and plasma of patients with gastric cardia adenocarcinoma (GCA) and dysplasia. Design and methods: Nested MSP approach was used to detect HLTF methylation status. Results: The frequency of HLTF methylation in high grade dysplasia and GCA tumor tissues was significantly higher than that in chronic inflammation tissues and was significantly associated with upper gastrointestinal cancers (UGIC) family history and protein and mRNA expression of the gene. HLTF methylation was not found in the plasma of patients with chronic inflammation and low grade dysplasia, while 4.0% (1/25) of patients with high grade dysplasia and 20.8% of (20/96) GCA patients were detected with hypermethylation of HLTF in the plasma. Conclusions: In all, HLTF methylation may exist in gastric cardia dysplasia stages and may play important role in the development of GCA especially in individuals with UGIC family history. [Copyright &y& Elsevier]

Abstract: Jak2/RUSH-mediated prolactin signaling culminates in RUSH-1α-DNA-binding. Heretofore, Jak2-specific phosphorylation residues in RUSH were unknown. Genpathway’s discovery approaches correlated RUSH-DNA binding (−126/−121) in uteroglobin’s proximal promoter with recruitment of the transcriptional machinery. NetPhos 2.0 server found a single tyrosine phosphorylation site in RUSH’s minimal DNA-binding domain. Y195 had identical context and prediction scores (0.52) for rabbit and human (HLTF) orthologs. The mouse ortholog (Hltf) had a higher prediction score (0.897). Affinity purified RUSHY195ph antibodies recognized native tyrosine phosphorylated RUSH protein immunoprecipitated from nuclear extracts. When R5020-treated HRE-H9 cells±the Jak2 inhibitor, Tyrene CR4, were stimulated with prolactin, confocal immunofluorescence images provided conclusive evidence that Jak2 mediated the availability of phosphorylated RUSHY195 in nucleus and cytoplasm. Catalytically active Jak2 is ipso facto a RUSH site-specific tyrosine kinase. Immunoprecipitation/Western blotting revealed both phosphorylation at Y195 and the physical interaction between p-Jak2/RUSH/HLTF/Hltf are evolutionarily conserved across three mammalian (rabbit, human, mouse) orthologs. [Copyright &y& Elsevier]

Abstract: DNA damage tolerance is regulated at least in part at the level of proliferating cell nuclear antigen (PCNA) ubiquitination. Monoubiquitination (PCNA-Ub) at lysine residue 164 (K164) stimulates error-prone translesion synthesis (TLS), Rad5-dependent polyubiquitination (PCNA-Ubn) stimulates error-free template switching (TS). To generate high affinity antibodies by somatic hypermutation (SHM), B cells profit from error-prone TLS polymerases. Consistent with the role of PCNA-Ub in stimulating TLS, hypermutated B cells of PCNA K164R mutant mice display a defect in generating selective point mutations. Two Rad5 orthologs, HLTF and SHPRH have been identified as alternative E3 ligases generating PCNA-Ubn in mammals. As PCNA-Ub and PCNA-Ubn both make use of K164, error-free PCNA-Ubn-dependent TS may suppress error-prone PCNA-Ub-dependent TLS. To determine a regulatory role of Shprh and Hltf in SHM, we generated Shprh/Hltf double mutant mice. Interestingly, while the formation of PCNA-Ub and PCNA-Ubn is prohibited in PCNA K164R MEFs, the formation of PCNA-Ubn is not abolished in Shprh/Hltf mutant MEFs. In line with these observations Shprh/Hltf double mutant B cells were not hypersensitive to DNA damage. Furthermore, SHM was normal in Shprh/Hltf mutant B cells. These data suggest the existence of an alternative E3 ligase in the generation of PCNA-Ubn. [Copyright &y& Elsevier]

Helicase-like transcription factor (HLTF) is a member of the SWI/SNF (mating type switching/sucrose non-fermenting) family of ATPases/helicases and also has a RING-finger motif characteristic of ubiquitin ligase proteins. These features have led to suggestions that HLTF functions like yeast Rad5, which promotes replication through DNA lesions via a post-replication repair pathway. However, the function of HLTF in higher eukaryotes is still unknown. Herein, we found the overexpression of HLTF in radiation recurrent human uterine cervical carcinoma tissues when compared to disease free survived patients tissues. In this study, we used RNA interference techniques to investigate the potential function of HLTF in cervical cancer cell line HeLa and found that the cell proliferation was reduced by knockdown (KD) of HLTF. A host-cell reactivation assay showed that the capacity for repair to DNA damage induced by X-ray irradiation was reduced in HLTF KD cells. X-rays also increased apoptosis in HLTF KD cells. These results suggest that HLTF is involved in DNA repair and apoptosis in cancer cells, which might represent a target for gene therapies of human cancer. [ABSTRACT FROM AUTHOR]

Abstract: Jak2/Stat-mediated prolactin signaling culminates in Stat5a-DNA-binding. However, not all Jak2-dependent genes have Stat5 sites. Western analysis with inhibitors showed Jak2 is a proximal intermediate in prolactin-induced RUSH phosphorylation. Transfection assays with HRE-H9 cells showed the RUSH-binding site mediated the ability of prolactin to augment progesterone-dependent transcription of the RUSH gene. Jak2 inhibitors or targeted RUSH-site mutation blocked the prolactin effect. RUSH co-immunoprecipitated with phospho-Jak2 from nuclear extracts. Jak2 inhibitors abolished the nuclear pool of phospho-RUSH not the nuclear content of RUSH in HRE-H9 cells. Nucleolar-affiliated partners, e.g. nucleolin, were identified by μLC/MS/MS analysis of nuclear proteins that co-immunoprecipitated with RUSH/GST-RING. RUSH did not exclusively co-localize with fibrillarin to the nucleolus. MG-132 (proteasomal inhibitor) failed to block Tyrene CR4-mediated decrease in phospho-RUSH, and did not promote RUSH accumulation in the nucleolus. These studies authenticate prolactin-dependent Jak2 phosphorylation of RUSH, and provide functional implications on the RUSH network of nuclear interactions. [Copyright &y& Elsevier]

Abstract: CHFR functions as a mitotic checkpoint by delaying entry into metaphase in response to mitotic stress. CHFR is frequently silenced by hypermethylation in human cancers, indicating that CHFR is a tumor suppressor. To further elucidate the role of CHFR in tumorigenesis, we studied the relationship between CHFR and a novel CHFR-interacting protein, HLTF, helicase-like transcription factor. Here we show that CHFR binds to and ubiquitinates HLTF, leading to its degradation. HLTF modulates basal expression of PAI-1 involved in regulation of cell migration. Consistently, overexpression of CHFR inhibits cell migration, resulting from reduced HLTF followed by decreased PAI-1 expression. HLTF expression is also higher in human breast cancer cells where CHFR is not expressed. Taken together, this is the first report identifying the regulatory mechanism of HLTF by CHFR, suggesting that CHFR-mediated downregulation of HLTF may help protect against cancer. [Copyright &y& Elsevier]

Aims: To examine the immunohistochemical expression of helicase-like transcription factor (HLTF) in relation to the prognosis of hypopharyngeal (HSCCs) and laryngeal (LSCCs) squamous cell carcinomas, and to characterize the HLTF protein variants expressed in biopsy specimens of head and neck squamous cell carcinoma (HNSCC) as well as the HeLa cell line. Methods and results: HLTF expression was determined by immunohistochemistry on a series of 100 hypopharyngeal (stage IV) and 56 laryngeal SCCs (stages I, II and IV). The HLTF variants were defined using reverse transcriptase-polymerase chain reaction and Western blots in 13 fresh HNSCC biopsies and in HeLa cells. High levels of HLTF expression were associated with rapid recurrence rates in a subgroup of 81 stage IV hypopharyngeal SCCs (with complete follow-up). A 95-kDa HLTF variant truncated at the carboxyl-terminal domain was detected in addition to the 115-kDa full-size protein in HNSCC biopsies, while six variants were observed in HeLa cells. Conclusions: Our results demonstrate, for the first time, that hypopharyngeal SCCs presenting high levels of HLTF have a worse prognosis. The quantitative determination of HLTF in hypopharyngeal SCCs was an independent prognostic marker alongside tumour node metastasis staging. HNSCCs expressed the truncated HLTF variant lacking the domains involved in DNA repair. [ABSTRACT FROM AUTHOR]

The helicase-like transcription factor (HLTF) belongs to the SWI/SNF family of chromatin-remodeling factors. Several SWI/SNF genes are disrupted in cancer, suggesting their possible role as tumor suppressors. Similarly, the HLTF gene was found to be inactivated by hypermethylation in a significant number of colon, gastric and uterine tumors, indicating that HLTF silencing may confer a growth advantage and that HLTF could be considered as a tumor suppressor gene. However, 20-fold HLTF overexpression was detected in various transformed cell lines, suggesting that HLTF could be associated with neoplastic transformation and act more like an oncogene. Moreover, HLTF activation was recently linked to the initial steps of carcinogenesis in an experimental model of estrogen-induced kidney tumors. Those apparently contradictory observations suggest that HLTF might play various roles in cancer. In this review, we will try to reconcile all these data in order to specify the role of HLTF in cancer progression. [ABSTRACT FROM AUTHOR]

PURPOSE and METHODS: In this study, we examined the combined methylation status of ITILTF, SOCS-1, and CDII /3 in 61 resected primary colorectal cancers using methylation-specific polymerase chain reaction and correlated the number of methylated genes with the clinicopathologic features of affected patients. RESULTS: We found a significant difference in lymph node metastasis (P = 0.020) when we compared the number of methylated genes in colorectal cancers with lymph node metastasis to those without it. CONCLUSIONS: Colorectal cancers without lymph node metastasis frequently exhibited the aberrant methylation of ITILTF, SOCS-1, and CDII13 genes. [ABSTRACT FROM AUTHOR]

HLTF is a pivotal protein in the template-switching pathway that allows DNA synthesis to continue even in the presence of DNA damage by utilizing a newly synthesized undamaged strand as a template. HLTF has a novel DNA-binding domain termed HIRAN that has been recently found in various proteins, although its detailed function remains unclear. In this study, the HIRAN domain of human HLTF was successfully crystallized. The crystals belonged to space group P41212 or P43212, with unit-cell parameters a = b = 130.0, c = 150.1 Å. [ABSTRACT FROM AUTHOR]

Abstract Background HLTF (Helicase-like Transcription Factor) is a DNA helicase protein homologous to the SWI/SNF family involved in the maintenance of genomic stability and the regulation of gene expression. HLTF has also been found to be frequently inactivated by promoter hypermethylation in human colon cancers. Whether this epigenetic event is required for intestinal carcinogenesis is unknown. Results To address the role of loss of HLTF function in the development of intestinal cancer, we generated Hltf deficient mice. These mutant mice showed normal development, and did not develop intestinal tumors, indicating that loss of Hltf function by itself is insufficient to induce the formation of intestinal cancer. On the Apcmin/+ mutant background, Hltf- deficiency was found to significantly increase the formation of intestinal adenocarcinoma and colon cancers. Cytogenetic analysis of colon tumor cells from Hltf -/-/Apcmin/+ mice revealed a high incidence of gross chromosomal instabilities, including Robertsonian fusions, chromosomal fragments and aneuploidy. None of these genetic alterations were observed in the colon tumor cells derived from Apcmin/+ mice. Increased tumor growth and genomic instability was also demonstrated in HCT116 human colon cancer cells in which HLTF expression was significantly decreased. Conclusion Taken together, our results demonstrate that loss of HLTF function promotes the malignant transformation of intestinal or colonic adenomas to carcinomas by inducing genomic instability. Our findings highly suggest that epigenetic inactivation of HLTF, as found in most human colon cancers, could play an important role in the progression of colon tumors to malignant cancer.

Lentiviruses, including HIV-1, possess the ability to enter the nucleus through nuclear pore complexes and can infect interphase cells, including those actively replicating chromosomal DNA. Viral accessory proteins hijack host cell E3 enzymes to antagonize intrinsic defenses, and thereby provide a more permissive environment for virus replication. The HIV-1 Vpr accessory protein reprograms CRL4 DCAF1 E3 to antagonize select postreplication DNA repair enzymes and activates the DNA damage checkpoint in the G2 cell cycle phase. However, little is known about the roles played by these Vpr targets in HIV-1 replication. Here, using a sensitive pairwise replication competition assay, we show that Vpr endows HIV-1 with a strong replication advantage in activated primary CD4 + T cells and established T cell lines. This effect is disabled by a Vpr mutation that abolishes binding to CRL4 DCAF1 E3, thereby disrupting Vpr antagonism of helicase-like transcription factor (HLTF) DNA helicase and other DNA repair pathway targets, and by another mutation that prevents induction of the G2 DNA damage checkpoint. Consistent with these findings, we also show that HLTF restricts HIV-1 replication, and that this restriction is antagonized by HIV-1 Vpr. Furthermore, our data imply that HIV-1 Vpr uses additional, yet to be identified mechanisms to facilitate HIV-1 replication in T cells. Overall, we demonstrate that multiple aspects of the cellular DNA repair machinery restrict HIV-1 replication in dividing T cells, the primary target of HIV-1 infection, and describe newly developed approaches to dissect key components., Competing Interests: The authors declare no conflict of interest., (Copyright © 2019 the Author(s). Published by PNAS.)

Summary To ensure the completion of DNA replication and maintenance of genome integrity, DNA repair factors protect stalled replication forks upon replication stress. Previous studies have identified a critical role for the tumor suppressors BRCA1 and BRCA2 in preventing the degradation of nascent DNA by the MRE11 nuclease after replication stress. Here we show that depletion of SMARCAL1, a SNF2-family DNA translocase that remodels stalled forks, restores replication fork stability and reduces the formation of replication stress-induced DNA breaks and chromosomal aberrations in BRCA1/2-deficient cells. In addition to SMARCAL1, other SNF2-family fork remodelers, including ZRANB3 and HLTF, cause nascent DNA degradation and genomic instability in BRCA1/2-deficient cells upon replication stress. Our observations indicate that nascent DNA degradation in BRCA1/2-deficient cells occurs as a consequence of MRE11-dependent nucleolytic processing of reversed forks generated by fork remodelers. These studies provide mechanistic insights into the processes that cause genome instability in BRCA1/2-deficient cells. [ABSTRACT FROM AUTHOR]

HLTF (helicase-like transcription factor) is a yeast RAD5 homolog found in mammals. HLTF has E3 ubiquitin ligase and DNA helicase activities, and plays a pivotal role in the template-switching pathway of DNA damage tolerance. HLTF has an N-terminal domain that has been designated the HIRAN (HIP116 and RAD5 N-terminal) domain. The HIRAN domain has been hypothesized to play a role in DNA binding; however, the structural basis of, and functional evidence for, the HIRAN domain in DNA binding has remained unclear. Here we show for the first time the crystal structure of the HIRAN domain of human HLTF in complex with DNA. The HIRAN domain is composed of six β-strands and two α-helices, forming an OB-fold structure frequently found in ssDNA-binding proteins, including in replication factor A (RPA). Interestingly, this study reveals that the HIRAN domain interacts with not only with a single-stranded DNA but also with a duplex DNA. Furthermore, the structure unexpectedly clarifies that the HIRAN domain specifically recognizes the 3'-end of DNA. These results suggest that the HIRAN domain functions as a sensor to the 3'-end of the primer strand at the stalled replication fork and that the domain facilitates fork regression. HLTF is recruited to a damaged site through the HIRAN domain at the stalled replication fork. Furthermore, our results have implications for the mechanism of template switching., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

Gastric cancer is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. Over 70% of new cases and deaths occur in developing countries. In the early years of the molecular biology revolution, cancer research mainly focuses on genetic alterations, including gastric cancer. Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression patterns in mammals. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Recent advancements in the rapidly evolving field of cancer epigenetics have shown extensive reprogramming of every component of the epigenetic machinery in cancer, including DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs, and microRNAs. Aberrant DNA methylation in the promoter regions of gene, which leads to inactivation of tumor suppressor and other cancer-related genes in cancer cells, is the most well-defined epigenetic hallmark in gastric cancer. The advantages of gene methylation as a target for detection and diagnosis of cancer in biopsy specimens and non-invasive body fluids such as serum and gastric washes have led to many studies of application in gastric cancer. This review focuses on the most common and important phenomenon of epigenetics, DNA methylation, in gastric cancer and illustrates the impact epigenetics has had on this field., (Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.)