| Structural highlights
Function
[CLSPN_HUMAN] Required for checkpoint mediated cell cycle arrest in response to inhibition of DNA replication or to DNA damage induced by both ionizing and UV irradiation. Adapter protein which binds to BRCA1 and the checkpoint kinase CHEK1 and facilitates the ATR-dependent phosphorylation of both proteins. Can also bind specifically to branched DNA structures and may associate with S-phase chromatin following formation of the pre-replication complex (pre-RC). This may indicate a role for this protein as a sensor which monitors the integrity of DNA replication forks.[1] [2] [3] [4] [5]
Publication Abstract from PubMed
Replisome disassembly is the final step of eukaryotic DNA replication and is triggered by ubiquitylation of the CDC45-MCM-GINS (CMG) replicative helicase(1-3). Despite being driven by evolutionarily diverse E3 ubiquitin ligases in different eukaryotes (SCF(Dia2) in budding yeast(1), CUL2(LRR1) in metazoa(4-7)), replisome disassembly is governed by a common regulatory principle, in which ubiquitylation of CMG is suppressed before replication termination, to prevent replication fork collapse. Recent evidence suggests that this suppression is mediated by replication fork DNA(8-10). However, it is unknown how SCF(Dia2) and CUL2(LRR1) discriminate terminated from elongating replisomes, to selectively ubiquitylate CMG only after termination. Here we used cryo-electron microscopy to solve high-resolution structures of budding yeast and human replisome-E3 ligase assemblies. Our structures show that the leucine-rich repeat domains of Dia2 and LRR1 are structurally distinct, but bind to a common site on CMG, including the MCM3 and MCM5 zinc-finger domains. The LRR-MCM interaction is essential for replisome disassembly and, crucially, is occluded by the excluded DNA strand at replication forks, establishing the structural basis for the suppression of CMG ubiquitylation before termination. Our results elucidate a conserved mechanism for the regulation of replisome disassembly in eukaryotes, and reveal a previously unanticipated role for DNA in preserving replisome integrity.
A conserved mechanism for regulating replisome disassembly in eukaryotes.,Jenkyn-Bedford M, Jones ML, Baris Y, Labib KPM, Cannone G, Yeeles JTP, Deegan TD Nature. 2021 Dec;600(7890):743-747. doi: 10.1038/s41586-021-04145-3. Epub 2021, Oct 26. PMID:34700328[6]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Chini CC, Chen J. Human claspin is required for replication checkpoint control. J Biol Chem. 2003 Aug 8;278(32):30057-62. Epub 2003 May 24. PMID:12766152 doi:http://dx.doi.org/10.1074/jbc.M301136200
- ↑ Lin SY, Li K, Stewart GS, Elledge SJ. Human Claspin works with BRCA1 to both positively and negatively regulate cell proliferation. Proc Natl Acad Sci U S A. 2004 Apr 27;101(17):6484-9. doi:, 10.1073/pnas.0401847101. Epub 2004 Apr 19. PMID:15096610 doi:http://dx.doi.org/10.1073/pnas.0401847101
- ↑ Sorensen CS, Syljuasen RG, Lukas J, Bartek J. ATR, Claspin and the Rad9-Rad1-Hus1 complex regulate Chk1 and Cdc25A in the absence of DNA damage. Cell Cycle. 2004 Jul;3(7):941-5. Epub 2004 Jul 13. PMID:15190204
- ↑ Sar F, Lindsey-Boltz LA, Subramanian D, Croteau DL, Hutsell SQ, Griffith JD, Sancar A. Human claspin is a ring-shaped DNA-binding protein with high affinity to branched DNA structures. J Biol Chem. 2004 Sep 17;279(38):39289-95. doi: 10.1074/jbc.M405793200. Epub 2004, Jun 28. PMID:15226314 doi:http://dx.doi.org/10.1074/jbc.M405793200
- ↑ Clarke CA, Clarke PR. DNA-dependent phosphorylation of Chk1 and Claspin in a human cell-free system. Biochem J. 2005 Jun 1;388(Pt 2):705-12. doi: 10.1042/BJ20041966. PMID:15707391 doi:http://dx.doi.org/10.1042/BJ20041966
- ↑ Jenkyn-Bedford M, Jones ML, Baris Y, Labib KPM, Cannone G, Yeeles JTP, Deegan TD. A conserved mechanism for regulating replisome disassembly in eukaryotes. Nature. 2021 Dec;600(7890):743-747. doi: 10.1038/s41586-021-04145-3. Epub 2021, Oct 26. PMID:34700328 doi:http://dx.doi.org/10.1038/s41586-021-04145-3
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