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XB-ART-53767
Mol Cell Biol 2016 Nov 14;3623:2983-2994. doi: 10.1128/MCB.00434-16.
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p97 Promotes a Conserved Mechanism of Helicase Unloading during DNA Cross-Link Repair.

Fullbright G , Rycenga HB , Gruber JD , Long DT .


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Interstrand cross-links (ICLs) are extremely toxic DNA lesions that create an impassable roadblock to DNA replication. When a replication fork collides with an ICL, it triggers a damage response that promotes multiple DNA processing events required to excise the cross-link from chromatin and resolve the stalled replication fork. One of the first steps in this process involves displacement of the CMG replicative helicase (comprised of Cdc45, MCM2-7, and GINS), which obstructs the underlying cross-link. Here we report that the p97/Cdc48/VCP segregase plays a critical role in ICL repair by unloading the CMG complex from chromatin. Eviction of the stalled helicase involves K48-linked polyubiquitylation of MCM7, p97-mediated extraction of CMG, and a largely degradation-independent mechanism of MCM7 deubiquitylation. Our results show that ICL repair and replication termination both utilize a similar mechanism to displace the CMG complex from chromatin. However, unlike termination, repair-mediated helicase unloading involves the tumor suppressor protein BRCA1, which acts upstream of MCM7 ubiquitylation and p97 recruitment. Together, these findings indicate that p97 plays a conserved role in dismantling the CMG helicase complex during different cellular events, but that distinct regulatory signals ultimately control when and where unloading takes place.

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Species referenced: Xenopus laevis
Genes referenced: brca1 cdc45 eif4g2 mcm2 mcm7

References [+] :
Akkari, DNA replication is required To elicit cellular responses to psoralen-induced DNA interstrand cross-links. 2000, Pubmed