Mechanism Of Cell Cycle Checkpoint Kinase 2 Phosphorylation Modified DNTP Hydrolase SAMHD1 To Regulate DNA Damage Repair

Objective:The balance of DNA damage response?DDR?is critical for genomic stability and maintenance of cellular homeostasis.Cell Cycle Checkpoint Kinase 2?Chk2?plays an important role in DNA damage and repair as an important member of the DNA damage repair response signaling pathway.The steady state of dNTPs is necessary to maintain accurate DNA replication and efficient DNA damage repair.SAMHD1,as the first dNTP hydrolase?dNTPase?found in mammals,is a key regulator of the dynamic balance of dNTP content in cells,suggesting that dNTP hydrolase SAMHD1 may be involved in DNA damage repair.Our recent work showed that DNA damage stimulation was induced in intestinal cancer HCT116 cells and mouse embryonic fibroblastic MEF cells,and the DNA damage repair-related marker proteins and SAMHD1phosphorylation levels were detected by Western Blotting,and SAMHD1 was identified in DNA damage repair response.DNA damage stimulation was applied to cells stably stabilizing and overexpressing SAMHD1 gene,and the regulation of SAMHD1 on DNA damage repair reaction was analyzed.By adding CHK2 small molecule inhibitor,it was confirmed that phosphorylation of SAMHD1 was regulated by CHK2 phosphorylation.The results indicate that CHK2 regulates DNA damage repair by phosphorylation of SAMHD1.This study explored the mechanism of CHK2 phosphorylation of dNTP hydrolase SAMHD1,regulates DNA damage repair,maintains genomic stability and cell homeostasis,and finds new intervention targets for clinical treatment of steady-state imbalance-related diseases.Methods:1.Using human colon cancer HCT116 cells and mouse embryonic fibroblastic MEF cells to induce DNA damage stimulation?Cisplatin,Etoposide,H₂O₂,DOX?,Western Blotting was used to detect DNA damage repair related marker proteins?ATM,P-ATM,CHK2,P-CHK2,?H2AX?and phosphorylation of the dNTP hydrolase SAMHD1,observed changes in phosphorylation levels of SAMHD1 during DNA damage repair.2 The role of SAMHD1 in DNA damage repair was determined by Western Blot analysis of the markers of DNA damage by administration of two DNA damage stimuli?Cisplatin,Etoposide?in cells silenced or overexpressed the SAMHD1gene.At the same time,the apoptosis level of silenced SAMHD1 cells and overexpressed SAMHD1 cells were detected by flow cytometry,and silenced SAMHD1 cells and overexpression of SAMHD1 were detected by real-time unlabeled cell analysis?RTCA?and cell counting.Cellular cell proliferation levels,clear SAMHD1 regulates DNA damage repair responses and cell fate decisions.In the cells stably stabilizing CHK2,the phosphorylation and DNA damage-related markers of SAMHD1 were detected by immunoprecipitation,and it was confirmed that the phosphorylation of SAMHD1 was regulated by CHK2 and regulated by DNA damage repair.By adding CHK2 small molecule inhibitor,it is clear that the phosphorylation of SAMHD1 is regulated by the phosphorylation of CHK2 T68.Res?lts:1.The phosphorylation of SAMHD1 was enhanced under DNA damage stimulation conditions.2.SAMHD1 is involved in the regulation of DNA damage repair responses and cell fate decisions.3.During DNA damage repair,CHK2 can regulate DNA damage repair by phosphorylation of SAMHD1.Conclusion:Cell cycle checkpoint kinase 2 can regulate DNA damage repair response by phosphorylation of SAMHD1.