The early studies showed the serine/threonine of OGG1 was phosphorylated by CDK4 in vitro, in our study, LC-MS/MS was performed, and Byonic engine was used to identify the precise site to be phosphorylated by CDK4.The present study discovered a high basal level of CDK4-mediated phosphorylation of OGG1 at S326, and this modification undergoes decline to resume a higher affinity with DNA for facilitating the role of OGG1 in gene transcription.