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The human nuclear co-repressor 2 (N-CoR2)gene (NCOR2,previously called silencing mediator for retinoid and thyroid hormone receptor SMRT)is recruited to nuclear and non-nuclear receptors in a large repressing complex containing also N-CoR1,mSin3 and HDACs.This large complex represses transcription in absence of ligand.Herein we report the high- resolution and refined mapping of NCOR2 at the boundary of sub-bands 12q24.23 and 12q24.31,and its intron/exon struc- ture.The gene contains 45 exons.This information should allow further study of potential NCOR2 genomic alteration in some subsets of malignancies. [ABSTRACT FROM AUTHOR]

The effect of DNA tertiary structure on modification by 4-acetoxy-aminoquinoline-l-oxide (Ac-4-HAQO) was investigated. The reactivity of pAT153 plasmid DNA depended on the conformational state of the molecule: it progressively decreased according to the decrease of the superhelical tension, being negatively supercoiled DNA about two times more susceptible than singly-nicked relaxed DNA. HPLC of the three main Ac-4-HAQO adducts showed that 3-(deoxyguanosin-N2-yl)-4-aminoquinoline-1-oxide, N-(deoxyguanosin-C8-yl)-4-aminoquinoline-l-oxide and 3-(deoxyadenosin-N6-yl)-4-aminoquinoline-l-oxide accounted for 50, 25 and 10% of total quinoline DNA base adducts in all DNA conformations tested, except in the negatively super-coiled topoisomers where they accounted for 80, 15 and 5% respectively. DNA modification by Ac-4-HAQO resulted also in the formation of apurinic/apyrimidinic sites and in strand scissions. The quantification of these damages revealed that they represent an important fraction of all damaging events and that their yield is also influenced by DNA superstructure. Thus, these lesions must be considered as important DNA damage induced by Ac-4-HAQO. [ABSTRACT FROM PUBLISHER]

2--H-Labelled 4-acetoxyaminoquinoline-1-oxide (Ac-4 HAQO), the ultimate carcinogen model of 4-nitroquinoline-1-oxide, was reacted with native and denatured DNA. We found that Ac-4 HAQO is 2- to 3-fold more reactive than diAc-4 HAQO, another ultimate carcinogen model of 4 NQO which was previously studied [Galiègue . (1980) . . , 609, 383–391]. Ac-4 HAQO-modified DNA is thermally destabilized: when 1% of the bases of DNA were modified by Ac-4 HAQO, its melting temperature decreased 1.2°C. Enzymatic degradation of Ac-4 HAQO-modified native and denatured DNA's to nucleosides was performed. The hydrolysates were analyzed, first with a simple chromatographic system, and then by h.p.l.c. The compounds recovered from the modified polymers were characterized by h.p.l.c. and a variation in their respective amounts as a function of the secondary structure of DNA was observed. Especially, the N-(deoxyguanosin-(C-yl)-4-aminoquinoline-1-oxide, the so called dG III adduct, was recovered from DNA, and its amount was evaluated to be ˜ 3.5-fold greater in the case of denatured DNA than in the case of native DNA. [ABSTRACT FROM PUBLISHER]

Hairy cell leukemia (HCL) is an indolent malignancy of mature B-lymphocytes. While existing front-line therapies achieve excellent initial results, a significant number of patients relapse and become increasingly treatment resistant. A major molecular driver of HCL is aberrant interlocking expression of the transcription factor JunD and the intracellular signaling molecule RhoH. Here we discuss the molecular basis of how the JunD-RhoH axis contributes to HCL pathogenesis. We also discuss how leveraging the JunD-RhoH axis identifies CD23, CD38, CD66a, CD115, CD269, integrin β7, and MET as new potential therapeutic targets. Critically, preclinical studies have already demonstrated that targeting CD38 with isatuximab effectively treats preexisiting HCL. Isatuximab and therapeutics directed against each of the other six new HCL targets are currently in clinical use to treat other disorders. Consequently, leveraging the JunD-RhoH axis has identified a battery of therapies that could be repurposed as new means of treating relapsed or refractory HCL.

The RhoH protein is a member of the Ras superfamily of guanosine triphosphate-binding proteins. RhoH is an atypical Rho family member that is always GTP-bound and thus always activated. It is restrictively expressed in normal hematopoietic cells, where it is a negative regulator of cell growth and survival. We previously analyzed the RHOH gene structure and demonstrated that this gene is composed of 7 exons, one single encoding exon located at the 3' extremity of the gene, preceded by 6 noncoding exons. To further understand the transcription events associated with this gene, we performed full-length RNA-Seq on 12 B-cell lines. We identified new exons, new splice events and new splice sites, leading to the discovery of 38 RHOH mRNA molecules, 27 of which have never been described before. Here, we also describe new fusion transcripts. Moreover, our method allowed quantitative measurements of the different mRNA species relative to each other in relation to B-cell differentiation., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

RhoH is an unusual member of the Rho family of small GTP-binding proteins in that it lacks GTPase activity. Since the RhoH protein is constantly bound by GTP, it is constitutively active and controlled predominantly by changes in quantitative expression. Abnormal levels of RHOH gene transcripts have been linked to a range of malignancies including acute myeloid leukemia (AML). One of the hallmarks of AML is a block in the normal program of myeloid differentiation. Here we investigate how myeloid differentiation is controlled by the quantitative expression of RHOH . Our analysis demonstrates that increasingly mature myeloid cells express progressively lower levels of RHOH . However, as monocytic myeloid cells terminally differentiate into macrophages, RHOH expression is up-regulated. This up-regulation is not apparent in AML where myeloid differentiation is blocked at stages of low RHOH expression. Nevertheless, when the up-regulation of RHOH is forced, then terminal macrophage differentiation is induced and the Cdc42 and Wnt intracellular signalling pathways are repressed. These results indicate that RHOH induction is a driver of terminal differentiation and might represent a means of effecting AML differentiation therapy. The potential of this therapeutic strategy is supported by forced up-regulation of RHOH reducing the ability of AML cells to produce tumours in vivo ., Competing Interests: Carl S. Shelley is President and CEO of Leukemia Therapeutics, LLC that is developing novel treatments for AML based on targeting the molecular consequences of aberrant RHOH repression., (© 2020 The Authors. eJHaem published by British Society for Haematology and John Wiley & Sons Ltd.)

Mucosal melanoma represents one of the most highly metastatic and aggressive subtypes of melanoma. The biology of mucosal melanoma is poorly documented, and the lack of experimental models makes it difficult to design and test new therapies. Dogs are frequently affected by melanomas of the oral cavity, making spontaneous canine melanoma a potentially predictable model for their human counterpart. We recently established and characterized two new canine mucosal melanoma cell lines named OCR_OCMM1 and OCR_OCMM2. Here, we identified quiescent cancer stem cell (CSC) subpopulations in both canine cell lines that displayed similarities to human quiescent CSCs: canine melanoma CSCs had the ability to self-renew, produced nonstem cell (SC) progeny, and formed melanospheres that recapitulated the phenotypic profile of the parental tumor. These CSCs also formed melanoma in immunodeficient mice, and the inhibition of PI3K/AKT signaling expanded the CSC pool. A subset of non-CSCs transitioned to become CSCs. OCR_OCMM1 and OCR_OCMM2 displayed different CSC compartment behaviors in regard to their initial size and expansion abilities. Collectively, this study showed that the OCR_OCMM1 and OCR_OCMM2 canine melanoma cell lines are powerful cellular tools to study melanoma SCs, not only for mucosal but also for the more common human cutaneous melanoma.

Background: Metastatic melanoma is one of the most aggressive forms of cancer in humans. Among its types, mucosal melanomas represent one of the most highly metastatic and aggressive forms, with a very poor prognosis. Because they are rare in Caucasian individuals, unlike cutaneous melanomas, there has been fewer epidemiological, clinical and genetic evaluation of mucosal melanomas. Moreover, the lack of predictive models fully reproducing the pathogenesis and molecular alterations of mucosal melanoma makes its treatment challenging. Interestingly, dogs are frequently affected by melanomas of the oral cavity that are characterized, as their human counterparts, by focal infiltration, recurrence, and metastasis to regional lymph nodes, lungs and other organs. In dogs, some particular breeds are at high risk, suggesting a specific genetic background and strong genetic drivers. Altogether, the striking homologies in clinical presentation, histopathological features, and overall biology between human and canine mucosal melanomas make dogs invaluable natural models with which to investigate tumor development, including tumor ætiology, and develop tailored treatments., Methods: We developed and characterized two canine oral melanoma cell lines from tumors isolated from dog patients with distinct clinical profiles; with and without lung metastases. The cells were characterized using immunohistochemistry, pharmacology and genetic studies., Results: We have developed and immunohistochemically, genetically, and pharmacologically characterized. Two cell lines (Ocr_OCMM1X & Ocr_OCMM2X) were produced through mouse xenografts originating from two clinically contrasting melanomas of the oral cavity. Their exhaustive characterization showed two distinct biological and genetic profiles that are potentially linked to the stage of malignancy at the time of diagnosis and sample collection of each melanoma case. These cell lines thus constitute relevant tools with which to perform genetic and drug screening analyses for a better understanding of mucosal melanomas in dogs and humans., Conclusions: The aim of this study was to establish and characterize xenograft-derived canine melanoma cell lines with different morphologies, genetic features and pharmacological sensitivities that constitute good predictive models for comparative oncology. These cell lines are relevant tools to advance the use of canine mucosal melanomas as natural models for the benefit of both veterinary and human medicine.

Approximately 30% of the patients who fulfil the criteria of Waldenström's macroglobulinemia (WM) are diagnosed while asymptomatic (indolent), and will not require immediate therapy. Conversely, patients with a disease-related event will be considered for therapy. The physiopathology of these 2 groups remains unclear, and the mechanisms of progression from indolent to symptomatic WM have yet to be fully understood. Seventeen patients diagnosed with WM were included in this study, 8 asymptomatic WM (A-WM) and 9 symptomatic WM (S-WM). A differential analysis was performed on a first series of 11 patients and identified 48 genes whose expression separated samples from A- to S-WM. This gene signature was then confirmed on a second independent validation set of 6 WM. Within this expression profile, BACH2 , a B-cell transcription factor known to be a tumor suppressor gene, was found to be over-expressed in A-MW relatively to S-MW. We specifically over-expressed BACH2 in a WM-related cell line and observed a significant reduction of the clonogenic activity. To the best of our knowledge, we report for the first time a specific gene expression signature that differentiates A-WM and S-WM. Within this expression profile, BACH2 was identified as a candidate gene that may help to understand better the behavior of tumor cells in indolent WM., Competing Interests: CONFLICTS OF INTEREST No conflicts of interest.

Hairy cell leukemia (HCL) is characterized by underexpression of the intracellular signaling molecule RhoH. Reconstitution of RhoH expression limits HCL pathogenesis in a mouse model, indicating this could represent a new therapeutic strategy. However, while RhoH reconstitution is theoretically possible as a therapy, it is technically immensely challenging as an appropriately functional RhoH protein needs to be specifically targeted. Because of this problem, we sought to identify druggable proteins on the HCL surface that were dependent upon RhoH underexpression. One such protein was identified as CD38. Analysis of 51 HCL patients demonstrated that 18 were CD38-positive. Interrogation of the clinical record of 23 relapsed HCL patients demonstrated those that were CD38-positive had a mean time to salvage therapy 71 months shorter than patients who were CD38-negative. Knockout of the CD38 gene in HCL cells increased apoptosis, inhibited adherence to endothelial monolayers, and compromised ability to produce tumors in vivo. Furthermore, an anti-CD38 antibody proved effective against pre-existing HCL tumors. Taken together, our data indicate that CD38 expression in HCL drives poor prognosis by promoting survival and heterotypic adhesion. Our data also indicate that CD38-positive HCL patients might benefit from treatments based on CD38 targeting., (©2015 American Association for Cancer Research.)

SNP array (SNPa) was developed to detect copy number alteration (CNA) and loss of heterozygosity (LOH) without copy number changes, CN-LOH. We aimed to identify novel genomic aberrations using SNPa in 31 WM with paired samples. Methylation status and mutation were analyzed on target genes. A total of 61 genetic aberrations were observed, 58 CNA (33 gains, 25 losses) in 58% of patients and CN-LOH in 6% of patients. The CNA were widely distributed throughout the genome, including 12 recurrent regions and identified new cryptic clonal chromosomal lesions that were mapped. Gene set expression analysis demonstrated a relationship between either deletion 6q or gain of chromosome 4 and alteration of gene expression profiling. We then studied methylation status and sought for mutations in altered regions on target genes. We observed methylation of DLEU7 on chromosome 13 in all patients (n = 12) with WM, and mutations of CD79B/CD79A genes (17q region), a key component of the BCR pathway, in 15% of cases. Most importantly, higher frequency of ≥3 CNA was observed in symptomatic WM. In conclusion, this study expands the view of the genomic complexity of WM, especially in symptomatic WM, including a potentially new mechanism of gene dysfunction, acquired uniparental disomy/CN-LOH. Finally, we have identified new potential target genes in WM, such as DLEU7 and CD79A/B., (Copyright © 2013 Wiley Periodicals, Inc.)

Mutation of the MYD88 gene has recently been identified in activated B-cell-like diffuse cell lymphoma and enhanced Janus kinase/signal transducer and activator of transcription (JAK-STAT) and nuclear factor κB (NF-κB) signaling pathways. A whole exome-sequencing study of Waldenstrom macroglobulinemia (WM) suggested a high frequency of MYD88 L265P mutation in WM. The genetic background is not fully deciphered in WM, although the role of NF-κB and JAK-STAT has been demonstrated. We analyzed MYD88 mutation in exon 5 and characterized the clinical significance of this genetic alteration in 67 WM patients. Clinical features; immunophenotypic markers; and conventional cytogenetic, fluorescence in situ hybridization, and single nucleotide polymorphism array data were analyzed. MYD88 L265P mutation was acquired in 79% of patients. Overall, we have identified alteration of the MYD88 locus in 91% of WM patients, including 12% with gain on chromosome 3 at the 3p22 locus that included the MYD88 gene. Patients with absence of MYD88 mutation were WM characterized with a female predominance, a splenomegaly, gain of chromosome 3, and CD27 expression. Importantly, inhibition of MYD88 signaling induced cytotoxicity and inhibited cell growth of cell lines issued from patients with WM. In conclusion, these results confirm a high frequency of MYD88 L265P mutation in WM. The discovery of MYD88 L265P mutation may contribute to a better understanding of the physiopathogeny of WM.

RhoH is a member of the Rho family of small GTP-binding proteins that lacks GTPase activity. Since RhoH is constantly bound by GTP, it is thought to be constitutively active and controlled predominantly by changes in quantitative expression. RhoH is produced specifically in haematopoietic cells and aberrant expression has been linked to various forms of leukaemia. Transcription of the RHOH gene is the first level at which the quantitative levels of the RhoH protein are regulated. Previous studies have demonstrated that RHOH gene transcription is initiated by three distinct promoter regions designated P1, P2 and P3 that define the 5' end of exons 1, 2 and 4 respectively. In the present study we report that the P3 promoter is largely responsible for RHOH gene transcription in the B-lymphocytic cell line Raji. The P3 promoter contains a minimal promoter region and a repressor region extending from -236 to +67 and +68 to +245 respectively, relative to the 5' end of exon 4. Chromatin immunoprecipitation demonstrated that two AP1 (activator protein 1) sites in the minimal promoter region bind JunD. When JUND is overexpressed, the endogenous RHOH gene is repressed; however, when JUND is inhibited, expression of endogenous RHOH is induced both in the Raji cell line and AML (acute myeloid leukaemia) cells. In the HCL (hairy cell leukaemia) cell line JOK-1, induction of RHOH increases expression of the α isoform of protein kinase C. This downstream target of RHOH is also induced in AML cells by JUND inhibition. Collectively, these data indicate that JunD is an inhibitor of RHOH gene expression.

Single-nucleotide polymorphism array (SNPa) and array-based comparative genomic hybridization (aCGH) are among the most sensitive genomic high-throughput screening techniques used in the exploration of genetic abnormalities in Waldenström's macroglobulinemia (WM). SNP and aCGH allow the identification of copy number abnormalities (CNA) at the kilobase level thus identifying cryptic genetic abnormalities unseen by lower-resolution approaches such as conventional cytogenetic or fluorescence in situ hybridization (FISH). CNA were identified in nearly 80% of cases by aCGH that delineated in addition minimal altered regions. At gene level, remarkable findings affecting genes involved in the regulation of the NF-kB signaling pathways were identified, such as biallelic inactivation of TNFAIP3 and TRAF3. SNPa also allowed characterization of copy neutral losses such as uniparental disomies (UPD), which is an important and frequent mechanism of gene alteration in cancer cells. Herein, we summarize the current knowledge of WM genomic basis using these high-throughput techniques.

The cause of hairy cell leukemia (HCL) is unknown. Current treatments seem effective only for a limited period of time. In addition, a significant proportion of patients remain refractive to all treatment options. These considerations indicate the need to develop alternative therapeutic strategies for HCL. Here, we report that HCL is characterized by underexpression of RhoH. In vitro reconstitution of RhoH expression inhibits the aberrant adhesion and transendothelial migration that drives disease pathogenesis. In an in vivo model of HCL, RhoH reconstitution limits malignant progression and protects against mortality. These findings provide the proof of principle that RhoH reconstitution represents a potential new approach to the treatment of HCL.

The hematopoiesis-specific RhoH gene is thought to be deregulated in B-cell non-Hodgkin's lymphoma (B-NHL), by either a chromosomal translocation or mutations, which affect its 5' regulatory region. The encoded Rho protein, always GTP-bound in vivo, was hypothesized to behave as a Rac antagonist. Extensive expression analysis allowed the detection of RhoH transcripts in all hematopoietic lineages (lymphoid, erythroid, myeloid), with a high level in lymphoid cells. To initiate investigations on the molecular mechanisms that regulate RhoH gene expression, Race-PCR and primer extension were conducted in the B-cell line Raji, which allowed (i) the establishment of RhoH complex intron/exon organization and (ii) the detection of several transcription initiation sites. In addition, a high 5' end heterogeneity of RhoH mRNAs was observed, due to alternative splicing of some 5' exons and to the use of these different transcription start sites. RT-PCR analysis led to the identification of this 5' end heterogeneity in different hematopoietic lineages. Discrepancies were particularly observed between B and T cells, due to an alternative splicing of one 5' exon (1b), which might be an important element in RhoH gene regulation. Such specific features have never been described for any Rho family member gene. They provide a molecular basis to study complex mechanisms involved in the control of RhoH expression.

The LAZ3(BCL6) gene on chromosome band 3q27 is nonrandomly disrupted in B-cell non-Hodgkin lymphoma (B-NHL) by chromosomal translocations clustered within a 3.3-kb MTC (major translocation cluster) located between the two first noncoding exons. These translocations generally result in the expression of a chimeric mRNA transcript between the LAZ3 gene and sequences derived from the partner chromosome. Using RACE RT-PCR, we previously demonstrated fusion of LAZ3 with the RhoH/TTF gene, a hemopoietic cell-specific small GTPase involved in cytoskeleton organization, and with the BOB1/OBF1 gene, a B-cell-specific coactivator of octamer-binding transcription factors, following translocations t(3;4)(q27;p13) and t(3;11)(q27;q23), respectively. Here we report the identification of the L-Plastin(LCP1) gene as a novel LAZ3 partner in chimeric transcripts resulting from a t(3;13)(q27;q14) translocation, in two cases of B-cell lymphoma. As a consequence of the translocation, the 5' regulatory region of each gene was exchanged, creating both LCP1-LAZ3 and reciprocal LAZ3-LCP1 fusion transcripts in one case, and only a LCP1-LAZ3 fusion transcript in the other. The 13q14 chromosome region is frequently disrupted in various proliferative disorders, and the LCP1 gene defines a new breakpoint site in this region. This gene encodes an actin-binding protein and is the second LAZ3 partner gene, with the RhoH/TTF gene, involved in actin cytoskeleton organization. Genes Chromosomes Cancer 26:97-105, 1999., (Copyright 1999 Wiley-Liss, Inc.)

We report four cases of follicular lymphoma with both t(14;18)(q32;q21) and the newly characterized t(3;4)(q27;p13). Molecular investigation confirmed LAZ3 (BCL6) rearrangement for all patients. The 3q27 aberrations have been rarely described in low-grade lymphomas and may represent secondary events whose implication remains to be elucidated.

Three cases of (3;13)(q27;q14) translocation observed in different histological types of non-Hodgkin lymphomas (NHLs) are reported here. This new recurring translocation in NHL was secondary in at least two of the patients because it was associated with another specific change [i.e., t(8;14) (q24;q32) in Burkitt lymphoma and t(14;18)(q32;q21) in typical follicular lymphoma]. In two of the cases for which molecular analysis was performed, a rearrangement of the LAZ-3/BCK-6 gene was found.

The LAZ3/BCL6 gene on chromosone 3q27 is recurrently disrupted in B cell non-Hodgkin's lymphomas by translocations involving immunoglobulin genes or other chromosone regions. We have cloned the breakpoint region and chromosone derivatives of the t(3;11)(q27;q23.1) translocation, present in a B cell leukemia cell line (Karpas 231), which define a novel 11q23.1 breakpoint site. As a consequence of the translocation, LAZ3 regulatory regions upstream of non-coding exon 2 are replaced by those of BOB1/OBF1, a recently described B cell-specific coactivator of octamer-binding transcription factors. A detailed structural study of the BOB1/OBF1 genomic DNA and of a nearly full-length cDNA revealed particular features in the 3' untranslated region, such as an Alu motif and a polymorphic tetranucleotide microsatellite. Two mutations leading to two potential amino acid changes in the C-terminal region, were also detected in one allele of a lymphoma B cell line, Raji. Due to its cell-specific expression and role as a coactivating transcription factor, chromosomal translocation and/or point mutation of BOB1/OBF1 may contribute to B cell tumorigenesis.

The LAZ3/BCL6 gene on chromosome 3q27 is recurrently disrupted in B-cell non Hodgkin's lymphomas by translocations involving immunoglobulin genes or other chromosome regions. We have studied the t(3; 11) (q27; q23) translocation, present in a B-cell leukemia cell line (Karpas 231). As a consequence of this translocation, a LAZ3 chimeric transcript was created by fusion, 5' to the LAZ3 exon 2, with a transcribed sequence identical to BOB1/OBF1, a B cell-specific coactivator of octamer-binding transcription factors, recently described. Nucleotidic sequence of a nearly full-length cDNA of the BOB1/OBF1 gene revealed particular features in the 3' untranslated region of the gene, including pyrimidine-rich sequence repeats, an Alu motif, and a polymorphic [CCTT] tetranucleotide microsatellite. Two A to G transition mutations were also detected in the coding region of one allele of a lymphoma B-cell line, Raji, leading to 2 amino-acid changes in the C-terminal region. Due to its cell-specificity and role as a coactivating transcription factor, chromosomal translocation and/or perhaps point mutation of BOB1/OBF1 may contribute to B cell tumorigenesis.

We have previously shown that the LAZ3/BCL6 gene encoding a potential transcription factor, is disrupted in B-diffuse large cell non-Hodgkin's lymphomas (NHL) with 3q27 chromosomal abnormalities involving the immunoglobulin (IG) genes. However, LAZ3 rearrangement also occurs in NHL bearing 3q27 translocations without involvement of the IG genes: for example the VAl cell line exhibits t(3;4)(q27;p11). In the present work we have used a RT-PCR method to detect and to sequence the LAZ3 mRNA products from the VAL cell line. We report that the consequence of the t(3;4) is the expression of a chimeric transcript of LAZ3 with a new gene encoding a small G-like protein, termed TTF (Translocation Three Four). Nucleotide sequence analysis of a 1.4 kb cDNA predicts that the TTF gene encodes a protein of 191 amino-acids similar to members of the RAS superfamily including HRAS (27% identical), RAB1A (30% identical) and RHO proteins: the human RAC1, RHOB and CDC42Hs proteins (respectively 43, 44 and 45% identical) and the yeast RHO2 protein (44% identical). Unlike most other small G proteins which are expressed ubiquitously, TTF was transcribed only in hemopoietic cells as a 2.2 kb transcript. TTF may define a new subgroup of RHO-like proteins.

In B-cell malignancies, the t(11;14)(q13;q32) at the 11q13 BCL1 locus is characterized by a scattering of breakpoint sites along a 100 kb genomic region, between the BCL1 major translocation cluster (MTC) and the PRAD1 (also termed cyclin D1 or CCND1) gene. Recently, the 11q13 breakpoint region was extended on both sides, centromeric to the MTC and telomeric to PRAD1. We report here the molecular cloning of a new t(11;14) breakpoint site, 20 kb centromeric to the MTC, from a patient with prolymphocytic leukemia. We subcloned a non-repetitive DNA fragment near the breakpoint and mapped this new 11q13 probe (pHO11c) relative to already identified breakpoint sites, using long- and short-range physical mapping within the BCL1 locus. Rearrangements in the BCL1 locus are associated with deregulation of the PRAD1 gene, which is often overexpressed, particularly in mantle-cell malignancies. The detectable but weak PRAD1 expression in the case we present suggests that this breakpoint centromeric to the MTC still lies inside the BCL1 locus boundaries. We think that attention should be focused on this region centromeric to the BCL1-MTC, where the investigation of previously unidentified translocations may increase understanding of the PRAD1 gene deregulation in t(11;14) associated pathologies.

The ETS family proteins have a conserved DNA-binding domain and act as transcription factors. Three domains have been recently defined in human ETS-1 proteins and their role could depend upon the nature of alternative transcripts according to whether they possess or lack DNA binding and/or transcriptional activation domain and also point mutation that could affect these important domains. Expression of ETS-1 gene is very complex and is controlled at several levels: the initiation of transcription, alternative splicing, post-translational modification, and protein stability. As a selection apparently exists for ETS-1 gene activation in hematopoietic cells, we investigated a relation between quantitative and qualitative ETS-1 expression and leukemogenesis. Using Northern blot, polymerase chain reaction (PCR), and single strand conformation polymorphism (SSCP) methods, we analyzed quantitative and qualitative ETS-1 expression in a variety of hematological pathologies and cell lines of different origin. Two ETS-1 transcripts of 6.8 and 2.7 kb, resulting from differential polyadenylation site utilization and exhibiting different stability, were observed. We identified, in a great number of patients, the four alternative ETS-1 products, but the relative extent significance of the four transcripts was very different from one patient to another. A non-conservative mutation observed in one case of T-cell acute lymphoblastic leukemia (T-ALL) and in the ETS-1 transactivation domain raised the question of suppressor activity for some ETS-1 products, as it is now known that activators and repressors can be encoded by the same gene and consistently co-expressed in vivo.

When the chemical carcinogen 4-nitroquinoline 1-oxide binds to DNA in vitro, two major adducts are formed, both at guanine residues, but at different positions, i.e. the C8 or the N2 position. Well-defined adducts (either C8 or N2 guanine adducts) can be formed in vitro by reacting DNA with 4-actoxyaminoquinoline 1-oxide (Ac-4HAQO) under different reaction conditions. Forward mutations induced by each of both main 4NQO adducts in the tetracycline resistance gene of pBR322 were determined. In total, 30 independent 4NQO-induced mutations were characterized, showing mainly base-pair substitution mutations and some frameshift mutations. We have observed that the 5' neighbouring base influences the specificity of dGuo-N2-AQO induced base-pair substitutions mutagenesis; a similar effect does not occur with dGuo-C8-AQO. This study reveals the importance of the N2 guanine adduct in the mutagenesis induced by 4NQO in vivo.

Duplex unwinding associated with DNA modification by 4-acetoxyaminoquinoline-1-oxide, a model ultimate carcinogen of 4-nitroquinoline-1-oxide, has been determined by the agarose gel electrophoresis band-shift method. An average unwinding angle per stable adduct of -15.1 degrees +/- 1.5 degrees for negatively supercoiled topoisomers and -6.5 degrees +/- 1.4 degrees for positively supercoiled topoisomers was obtained. Because of the different proportion of stable adducts (dGuo-N2-AQO, dGuo-C8-AQO, dAdo-N6-AQO) between negatively (8:1.5:0.5) and positively (5:2.5:1) supercoiled topoisomers, the difference in unwinding angles is suggestive of a diverse contribution of the various adducts to the overall conformational change. Since the largest unwinding angle was coupled with the highest proportion of dGuo-N2-AQO adduct, it is likely that this adduct is the most distortive lesion. A contribution of sites of base loss to DNA unwinding was also observed.

A comparison of the mutagenic potency of the N2 and the C8 guanylarylation of DNA by 4-nitroquinoline 1-oxide (4NQO) was established. The induced mutagenicity by the N2 guanine adduct is dependent on the SOS functions in the host and requires the umuC gene product. This lesion is repaired by the excision repair system and efficiently blocks the replication machinery. The data obtained with the C8 adduct show that this lesion is weakly toxic in the wild-type strain Escherichia coli probably because the efficiency of the replication is affected. This adduct is three times less mutagenic than the N2 adduct. These results suggest that in vivo the high mutagenicity of 4NQO can mainly be ascribed to the N2 guanine adduct.

Alkaline pH treatment of N-(deoxyguanosin-8-yl)-4-amino-quinoline 1-oxide forms two quinoline derivatives. The two compounds were analyzed together by mass and 500 MHz 1H-n.m.r. spectroscopies and were identified as two 7,8-guanine ring-opened rotamers: 1-(1'-deoxyriboside)-1-[6-(2,5-diamino-4-oxo-pyrimidinyl)]-3-(4-quino linyl 1-oxide) urea.

Native and denatured DNAs and polynucleotides were modified by 4-acetoxyaminoquinoline-1-oxide, the ultimate carcinogen of 4-nitroquinoline-1-oxide (4 NQO). The N-( deoxyguanosin -C8-yl)-4-aminoquinoline-1-oxide adduct, the so-called "dG III," was quantified on the DNA and on poly(dG-dC) in absorption spectroscopy, by using a spectral property of dG III, i.e., the variation of the absorption spectrum as a function of the pH. Using the "free-dG III" absorption reference spectra, a simple graphic determination of the percentage of dG III was established by recording the absorption spectra of the 4-acetoxyaminoquinoline-1-oxide-modified polymers. It was found that the dG III adduct accounts for about 30% of the total modification in the case of native modified DNA and poly(dG-dC) and for about 70% in the case of denatured modified DNA.

In vivo 4-hydroxyamino[2-3H]quinoline 1-oxide-modified DNA and in vitro 4-acetoxyamino[2-3H]quinoline 1-oxide-modified DNA were enzymatically hydrolyzed, and the hydrolysates were analyzed by high-performance liquid chromatography. The two patterns were compared, and we showed that all of the high-performance liquid chromatography peaks which were recovered from in vivo-modified DNA were present in the hydrolysate of in vitro-modified DNA. Therefore, we used the in vitro 4-acetoxyamino[2-3H]quinoline 1-oxide-modified DNA to investigate the quinoline-purine adducts which are characteristics of the mode of action of the carcinogen 4-nitroquinoline 1-oxide. By comparison with the enzymatic hydrolysates of 4-acetoxyamino[2-3H]quinoline 1-oxide-modified covalent poly(deoxyadenylate-deoxythymidylate) X poly(deoxyadenylate-deoxythymidylate) and covalent poly(deoxyguanylate-deoxycytidylate) X poly(deoxyguanylate-deoxycytidylate) three nitroquinoline adducts were enumerated on the modified DNA. One of them was previously characterized as a C8-guanyl adduct. We proved that the two other are a guanine and an adenine adduct, respectively. A quinoline derivative was identified in the hydrolysates of the in vivo- and in vitro-modified DNAs as 4-aminoquinoline 1-oxide, the origin of which was postulated to be a degradation compound of one (or more) adduct(s). Moreover, the presence of two degradation compounds of the C8-guanyl adduct was shown in mild alkaline conditions. We suspected an imidazole ring-opened form.

2-3H-Labelled 4-acetoxyaminoquinoline-1-oxide (Ac-4 HAQO), the ultimate carcinogen model of 4-nitroquinoline-1-oxide, was reacted in vitro with native and denatured DNA. We found that Ac-4 HAQO is 2- to 3-fold more reactive than diAc-4 HAQO, another ultimate carcinogen model of 4 NQO which was previously studied [Galiègue et al. (1980) Biochim. Biophys. Acta, 609, 383-391]. Ac-4 HAQO-modified DNA is thermally destabilized: when 1% of the bases of DNA were modified by Ac-4 HAQO, its melting temperature decreased 1.2 degrees C. Enzymatic degradation of Ac-4 HAQO-modified native and denatured DNA's to nucleosides was performed. The hydrolysates were analyzed, first with a simple chromatographic system, and then by h.p.l.c. The compounds recovered from the modified polymers were characterized by h.p.l.c. and a variation in their respective amounts as a function of the secondary structure of DNA was observed. Especially, the N-(deoxyguanosin-(C8-yl)-4-aminoquinoline-1-oxide, the so called dG III adduct, was recovered from DNA, and its amount was evaluated to be approximately 3.5-fold greater in the case of denatured DNA than in the case of native DNA.

Great quantities of chicken erythrocyte DNA with high levels of modification were obtained in vitro by reaction with 4-acetoxyaminoquinoline 1-oxide, a model ultimate carcinogen of 4-nitroquinoline 1-oxide. After enzymatic hydrolysis of the modified DNA, the three main adducts were separated and isolated by semipreparative high performance liquid chromatography. These three adducts were already characterized in vivo and in vitro in our previous work (S. Galiègue-Zouitina et al., Cancer Res., 45: 520-525, 1985). The structure of one of them was previously identified as N-(deoxyguanosin-8-yl)-4-aminoquinoline 1-oxide (B. Bailleul et al., Cancer Res., 41: 4559-4565, 1981). In this paper we have identified by mass spectroscopy and nuclear magnetic resonance the structures of the two other main adducts as 3-(deoxyguanosin-N2-yl)-4-aminoquinoline 1-oxide and 3-(deoxyadenosin-N6-yl)-4-aminoquinoline 1-oxide, respectively.