Expression And Regulation Of MiR-320Induced By Radiation And Its Function In The Radiation Response

MicroRNAs (miRNAs) are small single-stranded noncoding RNAs consisting of22nucleotides that play important gene-regulatory roles in eukaryotes by pairing to the mRNAs3'UTR to direct their posttranscriptional repression. MiRNAs are involved in a variety of ba-sic biological processes, such as cell proliferation, cell apoptosis and cell cycle arrest. In re-cent years, growing body of evidence indicates that miRNAs extensively participate in cellu-lar stress responses and play key roles in the biological effects of radiation. So miRNAs may serve as potential new targets for co-therapies aiming to improve the effects of radiation ther-apy in cancer patients.To identify miRNA induced by ionizing radiation (IR), we analyzed the expression pro-files of HeLa cells exposure to8Gy IR using miRNA microarrays and quantitative polyme-rase chain reaction with reverse transcriptase (qRT-PCR). We found that IR altered the ex-pression of many miRNAs significantly. In all of these IR-induced miRNAs, we identified that the expression of miR-320increased after IR in dose and time-dependent manner. In ad-dition, primary precursor form of miR-320(pri-miR-320) showed a similar change the same as the mature form. By GeneRacer assay we identified the transcriptional start site (TSS) of miR-320. By luciferase reporter assays and ChIP assays, we proved that pri-miR-320tran-scription regulated by the transcription factors-ATF2, ELK1, and YY1which were activated by p38MAPK and JNK when exposed to IR. We also identified that miR-320inhibited pro-liferation or colony formation and induced apoptosis through repressing its specific target genes.The main progresses were listed:1. MiRNA expression profile treated with8Gy IR. By using miRNA microarray and qRT-PCR, we showed that IR altered the expression of42miRNAs significantly. In all of these inducible miRNAs, we identified that miR-320and pri-miR-320expression linear increased after IR in dose and time-dependent manner.2. In the whole blood of Wistar rats and human, we identified that the expression of miR-320increased significantly with radiation dose and time exposure to IR. This implied that miR-320might act as a potential radiation biological dosimeter.3. ATF2, ELK1, and YY1were activated by p38MAPK and JNK exposure to IR and in-duced miR-320expression in HeLa cell line.4. MiR-320overexpression repressed its target genes including CDK6, XIAP, and HMGB1, which trigged G0/G1arrest, induced apoptosis and inhibited proliferation or colony for- mation.On the whole, we established ionizing radiation-induced miRNA expression profiling of HeLa cell line; revealed that miR-320expression linear increased after IR in dose and time-dependent manner; identified the TSS of miR-320and its transcription factors, signaling pathway and its target genes. Our work is of great importance in comprehensively elucidating the expression and function of miRNAs which involved in radiation-induced cellular res-ponses.