4.6 Article

Replication protein A dynamically regulates monoubiquitination of proliferating cell nuclear antigen

期刊

JOURNAL OF BIOLOGICAL CHEMISTRY
卷 294, 期 13, 页码 5157-5168

出版社

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.RA118.005297

关键词

proliferating cell nuclear antigen (PCNA); ubiquitin-conjugating enzyme (E2 enzyme); E3 ubiquitin ligase; ubiquitylation (ubiquitination); DNA damage; DNA replication; PCNA monoubiquitination; posttranslational modification (PTM); Rad6; Rad18; replication protein A (RPA); translesion DNA synthesis (TLS); DNA polymerase; DNA-binding protein; sliding clamp; cell cycle

资金

  1. National Institute of General Medical Sciences (NIGMS), National Institutes of Health [R01 GM013306]

向作者/读者索取更多资源

DNA damage tolerance permits bypass of DNA lesions encountered during S-phase and may be carried out by translesion DNA synthesis (TLS). Human TLS requires selective monoubiquitination of proliferating cell nuclear antigen (PCNA) sliding clamps encircling damaged DNA. This posttranslational modification (PTM) is catalyzed by Rad6/Rad18. Recent studies revealed that replication protein A (RPA), the major ssDNA-binding protein, is involved in the regulation of PCNA monoubiquitination and interacts directly with Rad18 on chromatin and in the nucleoplasm. However, it is unclear how RPA regulates this critical PTM and what functional role(s) these interactions serve. Here, we developed an in vitro assay to quantitatively monitor PCNA monoubiquitination under in vivo scenarios. Results from extensive experiments revealed that RPA regulates Rad6/Rad18 activity in an ssDNA-dependent manner. We found that DNA-free RPA inhibits monoubiquitination of free PCNA by directly interacting with Rad18. This interaction is promoted under native conditions when there is an overabundance of free RPA in the nucleoplasm where Rad6/Rad18 and a significant fraction of PCNA reside. During DNA replication stress, RPA binds the ssDNA exposed downstream of stalled primer/template (P/T) junctions, releasing Rad6/Rad18. RPA restricted the resident PCNAs to the upstream duplex regions by physically blocking diffusion of PCNA along ssDNA, and this activity was required for efficient monoubiquitination of PCNA on DNA. Furthermore, upon binding ssDNA, RPA underwent a conformational change that increased its affinity for Rad18. Rad6/Rad18 complexed with ssDNA-bound RPA was active, and this interaction may selectively promote monoubiquitination of PCNA on long RPA-coated ssDNA.

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