title: DNA.RNA helicase activity of RAD3 protein of Saccharomyces cerevisiae.
abstract: The RAD3 gene of Saccharomyces cerevisiae is required for excision repair of UV-damaged DNA and is essential for cell viability. The RAD3 protein exhibits a remarkable degree of sequence homology to the human excision repair protein ERCC2. The RAD3 protein is a single-stranded DNA-dependent ATPase and a DNA helicase capable of denaturing long regions of duplex DNA. Here, we demonstrate that RAD3 also possesses a potent DNA.RNA helicase activity similar in efficiency to its DNA helicase activity. The rad3 Arg-48 mutant protein, which binds but does not hydrolyze ATP, lacks the DNA.RNA unwinding activity, indicating a dependence on ATP hydrolysis. RAD3 does not show any RNA-dependent NTPase activity and, as expected, does not unwind duplex RNA. This observation suggests that RAD3 translocates on DNA in unwinding DNA.RNA duplexes. That the rad3 Arg-48 mutation inactivates the DNA and DNA.RNA helicase activities and confers a substantial reduction in the incision of UV-damaged DNA suggests a role for these activities in incision. We discuss how RAD3 helicase activities could function in tracking of DNA in search of damage sites and effect enhanced excision repair of actively transcribed genes.
authors.affiliation: Department of Biophysics, University of Rochester School of Medicine, NY 14642.
authors.forename: V
authors.initials: V
authors.lastname: Bailly
authors.forename: P
authors.initials: P
authors.lastname: Sung
authors.forename: L
authors.initials: L
authors.lastname: Prakash
authors.forename: S
authors.initials: S
authors.lastname: Prakash
mesh_terms: D000251:Adenosine Triphosphatases / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases / Q000378:metabolism*; D004260:DNA Repair; D006863:Hydrogen-Ion Concentration; D012313:RNA / Q000378:metabolism; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D013379:Substrate Specificity
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D012313:RNA; D000255:Adenosine Triphosphate; D004247:DNA; D012316:RNA Nucleotidyltransferases; D000251:Adenosine Triphosphatases; C061897:Rad3 protein, S cerevisiae; D004265:DNA Helicases; D020365:RNA Helicases