The DNA replication fork suppresses CMG unloading from chromatin before termination
Autor: | Gheorghe Chistol, Emily Low, Manal S. Zaher, Olga V. Kochenova, Johannes C. Walter |
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Rok vydání: | 2020 |
Předmět: |
DNA Replication
Chromosomal Proteins Non-Histone Xenopus Cell Cycle Proteins Xenopus Proteins law.invention Xenopus laevis 03 medical and health sciences chemistry.chemical_compound 0302 clinical medicine law Genetics Animals 030304 developmental biology 0303 health sciences Minichromosome Maintenance Proteins biology DNA synthesis Ubiquitination DNA replication Helicase DNA biology.organism_classification DNA Replication Fork Chromatin Recombinant Proteins Cell biology chemistry 030220 oncology & carcinogenesis biology.protein Recombinant DNA Research Paper Developmental Biology |
Zdroj: | Genes Dev |
ISSN: | 1549-5477 0890-9369 |
Popis: | When converging replication forks meet during replication termination, the CMG (Cdc45–MCM2–7–GINS) helicase is polyubiquitylated by CRL2Lrr1 and unloaded from chromatin by the p97 ATPase. Here, we investigate the signal that triggers CMG unloading in Xenopus egg extracts using single-molecule and ensemble approaches. We show that converging CMGs pass each other and keep translocating at the same speed as before convergence, whereafter they are rapidly and independently unloaded. When CMG unloading is blocked, diverging CMGs do not support DNA synthesis, indicating that after bypass CMGs encounter the nascent lagging strands of the converging fork and then translocate along double-stranded DNA (dsDNA). However, translocation on dsDNA is not required for CMG's removal from chromatin because in the absence of nascent strand synthesis, converging CMGs are still unloaded. Moreover, recombinant CMG added to nuclear extract undergoes ubiquitylation and disassembly in the absence of any DNA, and DNA digestion triggers CMG ubiquitylation at stalled replication forks. Our findings suggest that DNA suppresses CMG ubiquitylation during elongation and that this suppression is relieved when CMGs converge, leading to CMG unloading. |
Databáze: | OpenAIRE |
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