Study On The Effects Of OGG1 Single Nucleotide Mutations On Glycosidase Activity And Inflammatory Gene Expression

Reactive oxygen species?ROS?are produced all the time in cells.They at tack the proteins,lipids and DNA in cells and affect the metabolism of cells.Among the four bases of DNA,guanine G has the lowest potential and is mo st easily oxidized to 8-oxo-7,8-dihydroguanine?8-oxo G?.In order to maintain t he stability of genetic information in biological evolution,the 8-oxoG DNA gly cosylase?8-oxo G DNA glycosylase1,OGG1?in the body can carry out base e xcision repair?BER?for 8-oxo G.In addition,OGG1 can bind to 8-oxo G in or near the transcription factor recognition site under oxidative stress,thus regula ting the binding of transcription factors and gene expression.In recent years,four single nucleotide mutations of OGG1 have been found in different cancer patients:OGG1-R46Q,OGG1-R131Q,OGG1-R154H and OGG1-S326C.With the update of data,it is found that not only in the patients,but also in some healthy people,and those who carry the mutant have a higher risk of cancer.Earlier researchers found that the glycosidase activity of OGG1-R46Q purified in vitro had little change compared with that of wild-type;the glycosidase activity of OGG1-R154H purified in vitro decreased;the glycosidase activity of OGG1-S326C mutant decreased significantly in the state of oxidative stress.However,whether OGG1-R131Q glycoside hydrolase activity changes or not is not clear,and whether several mutants can promote transcription factors to combine with genes in the state of oxidative stress remains to be further determined.In order to further determine whether the functions of the four OGG1 mutants have changed,we constructed OGG1-R46Q,OGG1-R131Q,OGG1-R154H,OGG1-S326C plasmids.In vitro induction of protein purification combined with gel retardation migration test?EMSA?and DNA cutting?Cleavage?experiment showed that OGG1-R46Q and OGG1-S326C had similar glycoside hydrolase activity compared with wild type,OGG1-R131Q had almost no glucosidase activity,OGG1-R154H repair activity was weak,and immunofluorescence,PCR,chromatin immunoprecipitation?ChIP?and other experimental methods were used at cellular level.Now:the single nucleotide mutation of four sites does not affect the location of the protein in the nucleus;except OGG1-R131Q,three other mutants can promote the expression of Cxcl₂ gene,OGG1-R46Q and OGG1-R154H have the same effect as the wild type,but OGG1-S326C can continuously promote the gene expression within 120 minutes.These data suggest that single nucleotide mutations at 131 and 326 sites affect the function of OGG1.The abnormal expression of glycoside hydrolase activity and pro-inflammatory genes in OGG1 single nucleotide mutant may be related to the cancer susceptibility of the mutant carriers,which may provide a new direction for the research and prevention of related diseases.