期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 282, 期 39, 页码 28971-28979出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M705427200
关键词
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资金
- NIGMS NIH HHS [R01 GM071268, R01 GM071268-08, R01GM072569] Funding Source: Medline
Rmi1 is a conserved oligonucleotide and oligosaccharide binding-fold protein that is associated with RecQ DNA helicase complexes from humans (BLM-TOP3 alpha) and yeast (Sgs1-Top3). Although human RMI1 stimulates the dissolution activity of BLM-TOP3 alpha, its biochemical function is unknown. Here we examined the role of Rmi1 in the yeast complex. Consistent with the similarity of top3 Delta and rmi1 Delta phenotypes, we find that a stable Top3.Rmi1 complex can be isolated from yeast cells over-expressing these two subunits. Compared with Top3 alone, this complex displays increased superhelical relaxation activity. The isolated Rmi1 subunit also stimulates Top3 activity in reconstitution experiments. In both cases elevated temperatures are required for optimal relaxation unless the substrate contains a single-strand DNA (ssDNA) bubble. Interestingly, Rmi1 binds only weakly to ssDNA on its own, but it stimulates the ssDNA binding activity of Top3 5-fold. Top3 and Rmi1 also cooperate to bind the Sgs1 N terminus and promote its interaction with ssDNA. These results demonstrate that Top3-Rmi1 functions as a complex and suggest that Rmi1 stimulates Top3 by promoting its interaction with ssDNA.
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