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MicroRNAs (miRNA) are small RNA molecules that negatively regulate gene expression through base pairing interactions between 3'-UTR of the target mRNAs and seed sequence of miRNA. Any changes in the recognition site could destroy binding sites or modify binding affinity, resulting in evasion from miRNA regulation. A putative binding site for miR-491-5p resides in 3'-UTR of MMP9, and a genetic variant (rs1056628 A → C) is present in this region. The role of MMP9 over expression well marked in various cancers. However, whether rs1056628 SNP in miR-491-5p binding site of MMP9 3'-UTR could abrogate its post-transcriptional regulation and affect cancer susceptibility remains largely unknown. To test this, the rs1056628 SNP was genotyped in 300 cases of lung, gastric and breast cancers and 200 age- and sex-matched healthy controls. The results showed that compared with the AA genotype, C was a risk genotype for all three cancers development and was also associated with gastric and breast cancers metastasis and invasion. Based on the base pairing analysis and secondary structure evaluation of MMP9 mRNA and miR-491-5p, we found that miR-491-5p had a higher binding affinity for A genotype than the C genotype. The Luciferase activity of MMP9 3'-UTR indicates differential regulation of two genetic variations of MMP9. Overexpression of miR-491-5p decreased MMP9 mRNA level in cell lines of gastric, breast and lung cancers and thus leads to decreasing of the invasion ability. Therefore, for the first time we imply that the C variant of MMP9 contributes to the likelihood of gastric, breast and lung cancers susceptibility via a novel mechanism of subtle gene regulation through miRNA binding capacity.

Cleavage factor "CFIm25", as a key repressor at proximal poly (A) site, negatively correlates to cell proliferation and tumorigenicity in various cancers. Hence, understanding CFIm25 mechanism of action in breast cancer would be a great benefit. To this aim four steps were designed. First, potential miRNAs that target 3′-UtR of CFIm25 mRnA, retrieved from targetscan web server. Second, screened miRNAs were profiled in 100 breast cancer and 100 normal adjacent samples. Third, miRNAs that their expression was inversely correlated to the CFIm25, overexpressed in MDA-MB-231 cell line, and their effect on proliferation and migration monitored via MTT and wound healing assays, respectively. fourth, interaction of miRNAs of interest with 3′-UtR of CFIm25 confirmed via luciferase assay and western blot. our results indicate that CFIm25 considerably down-regulates in human breast cancer tissue. qRT-PCR assay, luciferase test, and western blotting confirm that CFIm25 itself could be directly regulated by oncomiRs such as miR-23,-24,-27,-135,-182 and-374. Besides, according to Mtt and wound healing assays of cell lines, CFIm25 knockdown intensifies cell growth, proliferation and migration. Our results also confirm indirect impact of CFIm25 on regulation of mRNA's 3′-UtR length, which then control corresponding miRNAs' action. miRNAs directly control CFIm25 expression level, which then tunes expression of the oncogenes and tumor proliferation. Therefore, regulation of CFIm25 expression level via miRNAs is expected to improve treatment responses in breast cancer. Abbreviations CPSF Cleavage and polyadenylation specificity factor CstF Cleavage stimulation factor PAS Polyadenylation site 3′-UTR 3′-Untranslated region UTR-APA Untranslated region-alternative polyadenylation miRNA/miR MicroRNA CFIm25 Cleavage factor Im 25 RF Random forest classifiers shRNA Short hairpin RNA HCC Hepatocellular carcinoma Living organisms apply complicated mechanisms of gene regulation to generate different cell types, which result in various behaviors from a single genome 1,2. Dynamic and highly polymorphic nature of mRNA polyadenylation, as a functional aspect of gene regulation, is one of the most recent discoveries in this field 3,4. Cleavage and polyadenylation of nascent mRNA accomplishes via application of two large multimeric complexes, which named as cleavage-polyadenylation specificity factor (CPSF) and cleavage stimulation factor (CstF), respectively. The

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