Survival of the Replication Checkpoint Deficient Cells Requires MUS81-RAD52 Function.
, Basile G
, Subramanyam S
, Malacaria E
, Bignami M
, Spies M
, Franchitto A
, Pichierri P
Section of Experimental and Computational Carcinogenesis, Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Rome, Italy.
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In checkpoint-deficient cells, DNA double-strand breaks (DSBs) are produced during replication by the structure-specific endonuclease MUS81. The mechanism underlying MUS81-dependent cleavage, and the effect on chromosome integrity and viability of checkpoint deficient cells is only partly understood, especially in human cells. Here, we show that MUS81-induced DSBs are specifically triggered by CHK1 inhibition in a manner that is unrelated to the loss of RAD51, and does not involve formation of a RAD51 substrate. Indeed, CHK1 deficiency results in the formation of a RAD52-dependent structure that is cleaved by MUS81. Moreover, in CHK1-deficient cells depletion of RAD52, but not of MUS81, rescues chromosome instability observed after replication fork stalling. However, when RAD52 is down-regulated, recovery from replication stress requires MUS81, and loss of both these proteins results in massive cell death that can be suppressed by RAD51 depletion. Our findings reveal a novel RAD52/MUS81-dependent mechanism that promotes cell viability and genome integrity in checkpoint-deficient cells, and disclose the involvement of MUS81 to multiple processes after replication stress.
PMID: 24204313 [PubMed - in process]