期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 376, 期 1, 页码 221-231出版社
ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2007.12.008
关键词
posttranslational protein modifications; SUMO; Ubc9; Siz1; PCNA
资金
- Cancer Research UK [A7123, A10152] Funding Source: Medline
Posttranslational modifications of proliferating cell nuclear antigen (PCNA), the eukaryotic processivity clamp for DNA polymerases, regulate the pathways by which replication problems are resolved. In the budding yeast Saccharomyces cerevisiae, ubiquitylation of PCNA in response to DNA damage facilitates the replicative bypass of lesions, whereas conjugation of the ubiquitin-related modifier (SUMO) prevents unscheduled crossover events during S phase. We have analyzed the SUMO modification pattern of budding yeast PCNA in vivo and in vitro and found that most aspects of our in vitro sumoylation reactions reflect the situation under physiological conditions. We show that two oligomeric SUMO chains of two to three moieties each, linked via internal sumoylation consensus motifs within the SUMO sequence, are assembled on PCNA. The SUMO-specific ligase Siz1 both stimulates the overall efficiency of sumoylation and selects the modification site on PCNA. Furthermore, ubiquitin and SUMO chains are assembled independently, and we found evidence that both modifiers can coexist in vivo on a common PCNA subunit. Our results demonstrate for the first time the in vivo assembly of polymeric SUMO chains of defined linkage on a physiological substrate in yeast, but they also indicate that SUMO-SUMO polymers are dispensable for PCNA(SUMO) function in replication and recombination. (C) 2007 Elsevier Ltd. All rights reserved.
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