The Mechanism Of OGG1 Involved In The Regulation Of Gene Expression By Regulating The Level Of H4R3me2a

DNA is the hereditary basis of lives.Its unique structure and extensive presence makes it be the most vulnerable target for DNA damage factors like reactive oxygen species(ROS).ROS,which characters as strong oxidizability and generating from various pathways,further attacks macromolecules like DNA and leads to oxidative stress.In this case,deoxyribose guanine(G)could be easily oxidized to 8-oxo-7-hydrodeoxyguanosine(8-oxodG)for its lowest redox potential,affecting DNA replication and even gene transcription.Several DNA repair systems were found to cope with this situation.And 8-oxodG can be specifically recognized and excised by the key enzyme in the Base Excision Repair(BER)system,named 8-Oxoguanine DNA Glycosylasel(OGG1).It has been reported that OGG1 not only take part in DNA repair,but in transcription regulation,like TNF,VEGF,etc.However,extensive work about OGG1-target-gene and related mechanisms still need to be studied to have a better understanding about OGG1.Histone arginine methylation is an important type of post-translational modification catalyzed by protein arginine N-methyltransferases(PRTMs).Previous wisdom have shown that methylated histone arginine residues would affect chromatin structure and recruit protein complexes to regulate transcription.In our work,we found that interplay between OGG1 and PRMT1 contribute in binding of PRMT1 to H4R3,resulting a difference in the level of H4R3me2a which is known for activating transcription.Considering this,we assume that OGG1 may regulate gene transcription via histone arginine methylation.In this paper,DNA microarray was performed among MEF WT and Ogg1-/-cell lines.On the base of the unique recognizing about OGG1 to 8-oxodG,we choose gene,which is rich in G in its promoter to do this study.Following experiments were conducted to support our hypothesis:Firstly,we tested the level of target gene in MEF WT and Ogg1-/-cell lines and found it only showed a significant difference under oxidative stress,we assume it may be resulted the signal of 8-oxodG induced by ROS.Secondly,it was reported that H4R3me2a could bind to the promoter region of genes.Based on our previous data that Ogg1-/-led to reduction of H4R3me2s,we explored whether Ogg1-/-still affect H4R3me2a.We further explore the relationship between OGG1 and H4R3me2a.As a result,we found OGG1 can regulate the level of H4R3me2a by participating the methylation of H4R3 via interacting with PRMT1,and this process was promoted under oxidative stress.We proposed that OGG1 regulate gene transcription via H4R3me2a.Then,we performed chromatin immunoprecipitation(CHIP)assay and revealed that OGG1 and H4R3me2a dramatically enriched in gene promoter region under oxidative stress.EMSA-electrophoretic mobility shift assay(EMSA)revealed that the existence of "8-oxodG" in target gene promoter can help bind OGG1.Streptavidin pull-down assay showed that "8-oxodG" contributed OGG1 and H4R3me2a binding to target gene promoter.In the end,Real-time PCR was used to test the level of target gene in knockdown PRMT1 cell line.Results showed significant reduction at both the gene level and H4R3me2a level.All the results above showed that OGG1 could regulate gene transcription through H4R3me2a.However,the following steps of how H4R3me2a activates gene expression is still unclear.We performed co-immunoprecipitation(Co-IP)and Streptavidin pull-down assay.We proposed that the complex of H4R3me2a-YY1 can bind to "8-oxodG" in target gene promoter to activate gene expression.We also made an exploration about the potential genes regulated by OGG1,like FEN1,and we that the mechanism about OGG1 regulating transcription may exist in other genes with abundant G in their promoters under oxidative stress.In a word,we propose that OGG1 is involved in gene transcriptional regulation via affecting H4R3me2a by recruiting PRMT1 under oxidative stress.Our work not only provide a novel mechanism for OGG1 regulating C-Myc,but also suggests the existence of a broader regulation pattern to replenish the OGG1-regulated genes.