BLM and RMI1 alleviate RPA inhibition of TopoIIIα decatenase activity.
RPA is a single-stranded DNA binding protein that physically associates with the BLM complex. RPA stimulates BLM helicase activity as well as the double Holliday junction dissolution activity of the BLM-topoisomerase IIIα complex. We investigated the effect of RPA on the ssDNA decatenase activity of topoisomerase IIIα. We found that RPA and other ssDNA binding proteins inhibit decatenation by topoisomerase IIIα. Complex formation between BLM, TopoIIIα, and RMI1 ablates inhibition of decatenation by ssDNA binding proteins. Together, these data indicate that inhibition by RPA does not involve species-specific interactions between RPA and BLM-TopoIIIα-RMI1, which contrasts with RPA modulation of double Holliday junction dissolution. We propose that topoisomerase IIIα and RPA compete to bind to single-stranded regions of catenanes. Interactions with BLM and RMI1 enhance toposiomerase IIIα activity, promoting decatenation in the presence of RPA.
Department of Biochemistry and Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada.
Jay
J
Yang
Csanad Z
CZ
Bachrati
Ian D
ID
Hickson
Grant W
GW
Brown
D002352:Carrier Proteins / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D029968:Escherichia coli Proteins / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism; D011485:Protein Binding; D053484:RecQ Helicases / Q000378:metabolism*; D051716:Replication Protein A / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D046912:Multiprotein Complexes; D051716:Replication Protein A; C476430:SSB protein, E coli; C097151:Bloom syndrome protein; D053484:RecQ Helicases; D004264:DNA Topoisomerases, Type I