title: Dss1 release activates DNA binding potential in Brh2.
abstract: Dss1 is an intrinsically unstructured polypeptide that partners with the much larger Brh2 protein, the BRCA2 ortholog in Ustilago maydis, to form a tight complex. Mutants lacking Dss1 have essentially the same phenotype as mutants defective in Brh2, implying that through physical interaction Dss1 serves as a positive activator of Brh2. Dss1 associates with Brh2 through an interaction surface in the carboxy-terminal region. Certain derivatives of Brh2 lacking this interaction surface remain highly competent in DNA repair as long as a DNA-binding domain is present. However, the Dss1-independent activity raises the question of what function might be met in the native protein by having Brh2 under Dss1 control. Using a set of Brh2 fusions and truncated derivatives, we show here that Dss1 is capable of exerting control when there is a cognate Dss1-interacting surface present. We find that association of Dss1 attenuates the DNA binding potential of Brh2 and that the amino-terminal domain of Brh2 helps evict Dss1 from its carboxy-terminal interaction surface. The findings presented here add to the notion that Dss1 serves in a regulatory capacity to dictate order in association of Brh2's amino-terminal and carboxy-terminal domains with DNA.
authors.affiliation: Department of Microbiology and Immunology and Weill Cornell Cancer Center, Weill Cornell Medical College, New York, New York 10065, United States.
authors.forename: Qingwen
authors.initials: Q
authors.lastname: Zhou
authors.forename: Milorad
authors.initials: M
authors.lastname: Kojic
authors.forename: William K
authors.initials: WK
authors.lastname: Holloman
mesh_terms: D004260:DNA Repair / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D005656:Fungal Proteins / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D014588:Ustilago / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins