Senescence-dependent MutS alpha dysfunction attenuates mismatch repair.
DNA damage and mutations in the genome increase with age. To determine the potential mechanisms of senescence-dependent increases in genomic instability, we analyzed DNA mismatch repair (MMR) efficiency in young and senescent human colonic fibroblast and human embryonic lung fibroblast. It was found that MMR activity is significantly reduced in senescent cells. Western blot and immunohistochemistry analysis revealed that hMSH2 and MSH6 protein (MutS alpha complex), which is a known key component in the MMR pathway, is markedly down-regulated in senescent cells. Moreover, the addition of purified MutS alpha to extracts from senescent cells led to the restoration of MMR activity. Semiquantitative reverse transcription-PCR analysis exhibited that MSH2 mRNA level is reduced in senescent cells. In addition, a decrease in E2F transcriptional activity in senescent cells was found to be crucial for MSH2 suppression. E2F1 small interfering RNA expression reduced hMSH2 expression and MMR activity in young human primary fibroblast cells. Importantly, expression of E2F1 in quiescent cells restored the MSH2 expression as well as MMR activity, whereas E2F1-infected senescent cells exhibited no restoration of MSH2 expression and MMR activity. These results indicate that the suppression of E2F1 transcriptional activity in senescent cells lead to stable repression of MSH2, followed by a induction of MutS alpha dysfunction, which results in a reduced cellular MMR capacity in senescent cells.
Chang
In-Youb
IY
Korean DNA Repair Research Center, Republic of Korea (South Korea).
Jin
Ming
M
Yoon
Sang Pil
SP
Youn
Cha-Kyung
CK
Yoon
Young
Y
Moon
Sung-Pyo
SP
Hyun
Jin-Won
JW
Jun
Jae Yeoul
JY
You
Ho Jin
HJ
D000818:Animals; D002460:Cell Line; D016922:Cellular Senescence; D053843:DNA Mismatch Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050687:E2F1 Transcription Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D007420:Intestine, Large / Q000378:metabolism; D051379:Mice; D051718:MutS Homolog 2 Protein / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D034622:RNA Interference
D004268:DNA-Binding Proteins; D050687:E2F1 Transcription Factor; C094443:G-T mismatch-binding protein; C102997:Msh6 protein, mouse; C497172:MSH2 protein, human; C497173:Msh2 protein, mouse; D051718:MutS Homolog 2 Protein