The RNA splicing factor ASF/SF2 inhibits human topoisomerase I mediated DNA relaxation.
Human topoisomerase I interacts with and phosphorylates the SR-family of RNA splicing factors, including ASF/SF2, and has been suggested to play an important role in the regulation of RNA splicing. Here we present evidence to support the theory that the regulation can go the other way around with the SR-proteins controlling topoisomerase I DNA activity. We demonstrate that the splicing factor ASF/SF2 inhibits relaxation by interfering with the DNA cleavage and/or DNA binding steps of human topoisomerase I catalysis. The inhibition of relaxation correlated with the ability of various deletion mutants of the two proteins to interact directly, suggesting that an interaction between the RS-domain of ASF/SF2 and a region between amino acid residues 208-735 on topoisomerase I accounts for the observed effect. Consistently, phosphorylation of the RS-domain with either topoisomerase I or a human cell extract reduced the inhibition of relaxation activity. Taken together with the previously published studies of the topoisomerase I kinase activity, these observations suggest that topoisomerase I activity is shifted from relaxation to kinasing by specific interaction with SR-splicing factors.
Andersen
Félicie F
FF
Department of Molecular and Structural Biology, University of Aarhus, C. F. Møllers Allé, Denmark.
Tange
Thomas Ø
TØ
Sinnathamby
Thayaline
T
Olesen
Jens R
JR
Andersen
Kirsten E
KE
Westergaard
Ole
O
Kjems
Jørgen
J
Knudsen
Birgitta R
BR
D002384:Catalysis; D004247:DNA / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000235:genetics; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D012326:RNA Splicing; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D059004:Topoisomerase I Inhibitors
D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D059004:Topoisomerase I Inhibitors; D000068103:Serine-Arginine Splicing Factors; D004247:DNA; D004264:DNA Topoisomerases, Type I