hMutS alpha is protected from ubiquitin-proteasome-dependent degradation by atypical protein kinase C zeta phosphorylation.
The hMutS alpha (hMSH2-hMSH6) protein heterodimer plays a critical role in the detection of DNA mispairs in the mismatch repair (MMR) process. We recently reported that hMutS alpha proteins were degraded by the ubiquitin-proteasome pathway in a cell-type-dependent manner, indicating that one or several regulator(s) may interfere with hMutS alpha protein ubiquitination and degradation. On the other hand, we and others have shown that protein kinase C (PKC) is involved as a positive regulator of MMR activity. Here, we provide evidence that the atypical PKC zeta regulates ubiquitination, degradation, and levels of hMutS alpha proteins. Using both PKC zeta-transfected U937 and PKC zeta siRNA-transfected MRC-5 cell lines, we found that PKC zeta protein expression was correlated with that of hMutS alpha as well as with MMR activity, but was inversely correlated with hMutS alpha protein ubiquitination and degradation. Interestingly, PKC zeta interacts with hMSH2 and hMSH6 proteins and phosphorylates both. Moreover, in an in vitro assay PKCzeta mediates phosphorylation events decreasing hMutS alpha protein degradation via the ubiquitin-proteasome pathway. Altogether, our results indicate that PKC zeta modulates hMutS alpha stability and protein levels, and suggest a role for PKC zeta in genome stability by regulating MMR activity.
Hernandez-Pigeon
Hélène
H
INSERM U563, CPTP, Bat B, Pavillon Lefebvre, Place du Dr Baylac, CHU PURPAN, BP 3028, 31024 Toulouse cedex 3, France.
Quillet-Mary
Anne
A
Louat
Thierry
T
Schambourg
Alexia
A
Humbert
Odile
O
Selves
Janick
J
Salles
Bernard
B
Laurent
Guy
G
Lautier
Dominique
D
D000964:Antimetabolites, Antineoplastic / Q000378:metabolism; D020137:Base Pair Mismatch; D002460:Cell Line; D002474:Cell-Free System; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D051718:MutS Homolog 2 Protein; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D013866:Thioguanine / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D000099221:Protein Kinase C zeta
D000964:Antimetabolites, Antineoplastic; D004268:DNA-Binding Proteins; D051718:MutS Homolog 2 Protein; D046988:Proteasome Endopeptidase Complex; D011493:Protein Kinase C; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D013866:Thioguanine; D025801:Ubiquitin; D000099221:Protein Kinase C zeta; C094443:G-T mismatch-binding protein; C497172:MSH2 protein, human