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Background: Y-box binding protein 1 (YB1 or YBX1) plays a critical role in tumorigenesis and cancer progression. However, whether YB1 affects malignant transformation by modulating non-coding RNAs remains largely unknown. This study aimed to investigate the relationship between YB1 and microRNAs and reveal the underlying mechanism by which YB1 impacts on tumor malignancy via miRNAs-mediated regulatory network., Methods: The biological functions of YB1 in hepatocellular carcinoma (HCC) cells were investigated by cell proliferation, wound healing, and transwell invasion assays. The miRNAs dysregulated by YB1 were screened by microarray analysis in HCC cell lines. The regulation of YB1 on miR-205 and miR-200b was determined by quantitative real-time PCR, dual-luciferase reporter assay, RNA immunoprecipitation, and pull-down assay. The relationships of YB1, DGCR8, Dicer, TUT4, and TUT1 were identified by pull-down and coimmunoprecipitation experiments. The cellular co-localization of YB1, DGCR8, and Dicer were detected by immunofluorescent staining. The in vivo effect of YB1 on tumor metastasis was determined by injecting MHCC97H cells transduced with YB1 shRNA or shControl via the tail vein in nude BALB/c mice. The expression levels of epithelial to mesenchymal transition markers were detected by immunoblotting and immunohistochemistry assays., Results: YB1 promoted HCC cell migration and tumor metastasis by regulating miR-205/200b-ZEB1 axis partially in a Snail-independent manner. YB1 suppressed miR-205 and miR-200b maturation by interacting with the microprocessors DGCR8 and Dicer as well as TUT4 and TUT1 via the conserved cold shock domain. Subsequently, the downregulation of miR-205 and miR-200b enhanced ZEB1 expression, thus leading to increased cell migration and invasion. Furthermore, statistical analyses on gene expression data from HCC and normal liver tissues showed that YB1 expression was positively associated with ZEB1 expression and remarkably correlated with clinical prognosis., Conclusion: This study reveals a previously undescribed mechanism by which YB1 promotes cancer progression by regulating the miR-205/200b-ZEB1 axis in HCC cells. Furthermore, these results highlight that YB1 may play biological functions via miRNAs-mediated gene regulation, and it can serve as a potential therapeutic target in human cancers., (© 2021 The Authors. Cancer Communications published by John Wiley & Sons Australia, Ltd. on behalf of Sun Yat-sen University Cancer Center.)

miRNAs are important regulators of eukaryotic gene expression. The post-transcriptional maturation of miRNAs is controlled by the Drosha-DiGeorge syndrome critical region gene 8 (DGCR8) microprocessor. Dysregulation of miRNA biogenesis has been implicated in the pathogenesis of human diseases, including cancers. C-terminal-binding protein-interacting protein (CtIP) is a well-known DNA repair factor that promotes the processing of DNA double-strand break (DSB) to initiate homologous recombination-mediated DSB repair. However, it was unclear whether CtIP has other unknown cellular functions. Here, we aimed to uncover the roles of CtIP in miRNA maturation and cancer cell metastasis. We found that CtIP is a potential regulatory factor that suppresses the processing of miRNA primary transcripts (pri-miRNA). CtIP directly bound to both DGCR8 and pri-miRNAs through a conserved Sae2-like domain, reduced the binding of Drosha to DGCR8 and pri-miRNA substrate, and inhibited processing activity of Drosha complex. CtIP depletion significantly increased the expression levels of a subset of mature miRNAs, including miR-302 family members that are associated with tumor progression and metastasis in several cancer types. We also found that CtIP-inhibited miRNAs, such as miR-302 family members, are not crucial for DSB repair. However, increase of miR-302b levels or loss of CtIP function severely suppressed human colon cancer cell line tumor cell metastasis in a mouse xenograft model. These studies reveal a previously unrecognized mechanism of CtIP in miRNA processing and tumor metastasis that represents a new function of CtIP in cancer., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

While some microRNAs are transcribed from a specific promoter, at least one third of human miRNA genes are clustered, wherein multiple miRNA genes are generated from a single primary transcript such as miR-17 ~ 92 cluster. Although six members of the cluster are generated from a single transcript, the mature level of each member may be diverse in various cell types. Here, we attempt to monitor the mature level of miR-17, miR-92a, and miR-20a from miR-17 ~ 92 cluster in blood (HL60 (human promyelocytic leukemia cells) and Jurkat) and breast (MDA-MB-231 and MCF-7) cancer cell lines. Interestingly, different mature levels of the miRNAs were observed in each cell line. While miR-20 was highly matured in HL60 and MDA-MB-231 cell lines, higher mature level of miR-92a was observed in Jurkat cell line compared to that of miR-20 and miR-17. Further, the mature level of miRNAs was also measured in normal and cancer cell lines. Although the mature level of miR-17 and miR-92a increased in HL60 and Jurkat cell lines, miR-20 expression showed an almost identical level in blood cancer cell lines compared to controls. Conversely, miR-20 mature level significantly increased in breast cancer cell lines whereas the expression level of miR-92a was comparable in MDA-MB-231, MCF-7, and MCF-10A cell lines.

The guardian of the genome p53 is embedded in a fine-spun network of MicroRNAs. p53 is able to activate or repress directly the transcription of MicroRNAs that are participating in the tumor-suppressive mission of p53. On the other hand, the expression of p53 is under tight control of MicroRNAs that are either targeting directly p53 or factors that are modifying its protein level or activity. Although the most important function of p53 is suggested to be transcriptional regulation, there are several nontranscriptional functions described. One of those regards the modulation of MicroRNA biogenesis. Wild-type p53 is increasing the maturation of selected MicroRNAs from the primary transcript to the precursor MiRNA by interacting with the Microprocessor complex. Furthermore, p53 is modulating the mRNA accessibility for certain MicroRNAs by association with the RISC complex and transcriptional regulation of RNA-binding proteins. In this way p53 is able to remodel the MiRNA-mRNA interaction network. As wild-type p53 is employing MicroRNAs to suppress cancer development, gain-of-function mutant p53 proteins use MicroRNAs to confer oncogenic properties like chemoresistance and the ability to drive metastasis. Like its wild-type counterpart mutant p53 is able to regulate MicroRNAs transcriptionally and posttranscriptionally. Mutant p53 affects the MiRNA processing at two cleavage steps through interfering with the Microprocessor complex and by downregulating Dicer and KSRP, a modulator of MiRNA biogenesis. Thus, MicroRNAs are essential components in the p53 pathway, contributing substantially to combat or enhance tumor development depending on the wild-type or mutant p53 context., (© 2017 Elsevier Inc. All rights reserved.)