title: Regulation of Metnase's TIR binding activity by its binding partner, Pso4.
abstract: Metnase (also known as SETMAR) is a SET and transposase fusion protein in humans and plays a positive role in double-strand break (DSB) repair. While the SET domain possesses histone lysine methyltransferase activity, the transposase domain is responsible for 5'-terminal inverted repeat (TIR)-specific binding, DNA looping, and DNA cleavage activities. We recently demonstrated that human homolog of Pso4 (hPso4) is a Metnase binding partner that mediates Metnase binding to non-TIR DNA such as DNA damage sites. Here we show that Metnase functions as a dimer in its TIR binding. While both Metnase and hPso4 can independently interact with TIR DNA, Metnase's DNA binding activity is not required for formation of the Metnase-hPso4-DNA complex. A further stoichiometric analysis indicated that only one protein is involved in interaction with dsDNA when Metnase-hPso4 forms a stable complex. Interaction of the Metnase-hPso4 complex with TIR DNA was competitively inhibited by both TIR and non-TIR DNA, suggesting that hPso4 is solely responsible for binding to DNA in the Metnase-hPso4-DNA complex. Together, our study suggests that hPso4, once it forms a complex with Metnase, negatively regulates Metnase's TIR binding activity, which is perhaps necessary for Metnase localization at non-TIR sites such as DSBs.
authors.affiliation: Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, 980 W. Walnut Street, Indianapolis, IN 46202, USA.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Beck
authors.forename: Sung S
authors.initials: SS
authors.lastname: Lee
authors.forename: Robert
authors.initials: R
authors.lastname: Hromas
authors.forename: Suk-Hee
authors.initials: SH
authors.lastname: Lee
mesh_terms: D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000502:physiology*; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism*; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D055029:Inverted Repeat Sequences / Q000502:physiology*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization / Q000502:physiology; D017434:Protein Structure, Tertiary; D000072260:RNA Splicing Factors
chemical_list: D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D000072260:RNA Splicing Factors; D004247:DNA; D011495:Histone-Lysine N-Methyltransferase; C510450:SETMAR protein, human; D045643:DNA Repair Enzymes; C417041:PRPF19 protein, human