Protein phosphatase PP4 is involved in NHEJ-mediated repair of DNA double-strand breaks.
Reversible phosphorylation is an essential posttranslational modification to turn on/off a protein function and to regulate many cellular activities, including DNA repair. A DNA double-strand break (DSB) is the most lethal form of DNA damage and is mainly fixed by the error-prone nonhomologous end joining (NHEJ)-mediated repair and by the high-fidelity homology recombination (HR)-mediated repair. We found previously that protein phosphatase PP4 is required for HR-mediated DSB repair. In this report, we showed that depletion of PP4C by siRNA compromised NHEJ-mediated repair of DSBs induced by the nuclease I-SceI. Both PP4C and its regulatory subunit PP4R2 physically interacted with the chromatin condensation factor KAP1 (KRAB-associated protein 1). Depletion of PP4C led to sustained phosphorylation of KAP1 at Ser824. Conversely, overexpression of PP4C resulted in a decrease of KAP1 phosphorylation. PP4 dephosphorylated pKAP1 in vitro. Inhibition of KAP1 expression resulted in a defect on NHEJ-mediated DSB repair, and co-depletion of PP4c and KAP1 did not have significant synergistic effect on NHEJ-mediated DSB repair. Taken together, our results suggest that PP4C and KAP1 are in the same epistasis group, and PP4 is involved in NHEJ-mediated DSB repair, possibly through regulating the phosphorylation status of KAP1.
Beijing Key Laboratory of DNA Damage Response and College of Life Science, Capital Normal University, Beijing, China.
Jinping
J
Liu
Linli
L
Xu
Jianing
J
Zhong
Ji
J
Liao
Jing
J
Li
Xingzhi
X
Xu
D002460:Cell Line; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000076183:Tripartite Motif-Containing Protein 28
D034741:RNA, Small Interfering; D012097:Repressor Proteins; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28; D010749:Phosphoprotein Phosphatases; C080406:protein phosphatase 4