The Study On A-I RNA Editing And Regulation Mechanism Of Cancer-related Genes, ARHGAP26and NEIL1

RNA editing is an important post-transcriptional regulation, in which A-I RNA editingis the most important and the most common types of RNAediting.ADAR1catalyzed theA-IRNAediting reaction. It could recognize specific double-stranded RNAstructure and mRNAprecusor, and deaminate adenosine (A) into hypoxanthine (I), which I usually will berecognited as G by ribosome. So it can result in the change of nucleic acid sequence andcodon. RNA editing can influence on many biological functions, such as the processingstability of mRNA and microRNA maturation and change the recognition of the substratetargeted by microRNA. Adenosine deaminase acting on RNA (ADAR) is the main editingenzyme that mediates and catalyzes RNA editing reaction. The known ADAR familycontains the four members, ADAR1, ADAR2, ADAR3and TADAR. Among four of them,ADAR1is the editing enzyme which has been studied widely. Modern high-throughputsequencing technology demonstrates that RNA editing widespreads in the human genome,mainly occurring in the repetition noncoding sequence of human genome and CDS region.The relationship between A-I RNA editing and human disease has been the research hotpotin this field. Increasing studies showed that A-I RNA editing was closely related to theformation and development of many kinds of cancers, such as liver cancer, skin cancer, braintumor and so on. Compared with the corresponding normal cells, the level of RNAediting incancer cells was significantly changed and imbalanced in the expression of editing enzymes.This study aims to make research on theA-I RNAediting event of cancer-related genes andto test the editing difference between the normal and cancer tissues, trying to do a tentativeexploration in the regulation mechanism of RNA editing and the influence of its potentialfunction.This study aims to make a tentative research on the A-I RNA editing on3’UTR oftumor suppressor gene ARHGAP26in brain tumor and coding region of gene NEIL1inleukocyte from leukemia patients and breast cancer cells. It was identified that the editing events of cancer-related genes ARHGAP26and NEIL1existed in the leukocyte fromleukemia patients and breast cancer cells. And then by comparing the editing level of thenormal and cancer cells, it was showed that the editing level of ARHGAP26in brain tumorwas significantly decreased and the editing frequency of NEIL1in leukocyte from leukemiapatients was significantly reduced and in breast cancer cells was lowered. So it wassuggested that there existed the editing difference between the normal and the cancer.According to this hint, we tried to reveal the regulation mechanism of cancer-related geneeditingevent andthe influenceonpotentialfunction.First of all, by experimental verification the A-I RNA editing events occurred in thebrain tumor cells and all editing sites located in the3’UTR region ofARHGAP26and therewas significant difference of editing level between brain tumor and normal tissues. Then wetested the expression of ARHGAP26protein, ADAR1and ADAR2in the brain tumor andnormal tissues. It was showed that compared with the corresponding normal tissues, theexpression of protein ARHGAP26and ADAR1in brain tumor was much lower, and theADAR2was a little lower.According to the experimental results, we suggested that in brainADAR1was the main editing enzyme of ARHGAP26and there potentially existed therelationship betweentheARHGAP26andADAR1andthebraintumor.In order to make further identification, we over-expressed and knocked down theexpression of ADAR1in astrocytoma glioma cell line U87. It was showed that when theADAR1expression was reduced, the editing level ofARHGAP26was much lower than thecontrol. While ADAR1was over-expressed, the editing level in U87became significantlyincreased. Moreover, there was no following change inADAR2expression during the aboveprocedures. Therefore, it was demonstrated that ADAR1catalyzed the process ofARHGAP26editing in brain.Last but not the least, we made some efforts on the editing event of DNArepair enzymegene NEIL1. Through experimental verification, the editing event of NEIL1in CDS regiontook place in leukocyte from leukemia patients. And compared with the normal blood cells,the editing level of NEIL1was much more reduced. Via analyzing24alternative splice isoforms, we explored the potential relationship between editing event and alternative spliceandtheirfunction influence,providing resourcesforthefurtherstudy.Based on this study, we propose the following views. The brain tumor is closely relatedwith the decrease of ARHGAP26editing and the aberrant expression of ADAR1, and inwhich ADAR1is the main editing enzyme of ARHGAP26. The editing event of NEIL1islikely to contribute to NEIL1biological activity by combining with the alternative spliceprocess. Our study focused on the abnormal editing event of cancer-related gene, providingtheorysupport forfurtherresearch oncancerinthefuture.