Investigation On Human MutT Homolog 2 Gene Transcriptional Regulation

Human MutT homolog 2(hMTH2),also known as NUDT15(nucleoside diphophate-linked moiety X-type motif),belongs to the Nudix hydrolase superfamily in cells.Removal of oxidized deoxyribonucleotides reduced DNA oxidation and reduced DNA mutation rates.MTH2 provided a protection mechanism for cells from DNA damage and would be used as a target for clinical treatment of tumors and other related diseases in the future.However,the regulation mechanism of the MTH2 gene itself is not yet clear.Based on the previous research of our laboratory,we will further explore the transcriptional regulation mechanism of MTH2 gene.We determined the transcriptional factors binding to the MTH2 gene promoter and their binding sites by bioinformatics analysis and molecular biology experiments.And it was further clarified the transcriptional regulation mechanism of the MTH2 gene promoter through overexpression and knocking down transcriptional factors.Firstly,dual luciferase detection kit was used to detect the the MTH2 promoter activity transfected with different cell lines.It has specific activities in liver cancer cells.Subsequently,the MTH2 gene promoter was subcloned with 5' deletions,and firefly luciferase reporter gene activities of each fragment of the MTH2 promoter were detected,and the minimal region for transcriptional regulation of the promoter was MTH2-176~+75.Then,by using software analysis including PROMO and TRANSFAC,the transcription factor binding sites in the minimal MTH2 promoter was predicted.Then the deletion mutation or point mutation constucts of the transcription factor binding sites were constructed,and the effects of the mutants on the promoter activities were detected.Pax4 and CREB1 overexpression vectors were constructs,and siRNA against transcription factors were used.The results showed that the deletion mutations and point mutations of Pax4 and CREB1 decreased the activities of MTH2 promoter.Overexpression of Pax4 and CREB1 increased the activities of MTH2 promoter,and increased the transcription and translation of MTH2.Knockdown of Pax4 and CREB1 expression,decreased MTH2 promoter luciferase activities,and decreased MTH2 transcription and translation levels.These results indicated that Pax4 and CREB1 directly bind to the MTH2 promoter,thereby regulating the transcription level of the MTH2 gene promoter.