title: Cockayne syndrome B protein stimulates apurinic endonuclease 1 activity and protects against agents that introduce base excision repair intermediates.
abstract: The Cockayne syndrome B (CSB) protein--defective in a majority of patients suffering from the rare autosomal disorder CS--is a member of the SWI2/SNF2 family with roles in DNA repair and transcription. We demonstrate herein that purified recombinant CSB and the major human apurinic/apyrimidinic (AP) endonuclease, APE1, physically and functionally interact. CSB stimulates the AP site incision activity of APE1 on normal (i.e. fully paired) and bubble AP-DNA substrates, with the latter being more pronounced (up to 6-fold). This activation is ATP-independent, and specific for the human CSB and full-length APE1 protein, as no CSB-dependent stimulation was observed with Escherichia coli endonuclease IV or an N-terminal truncated APE1 fragment. CSB and APE1 were also found in a common protein complex in human cell extracts, and recombinant CSB, when added back to CSB-deficient whole cell extracts, resulted in increased total AP site incision capacity. Moreover, human fibroblasts defective in CSB were found to be hypersensitive to both methyl methanesulfonate (MMS) and 5-hydroxymethyl-2'-deoxyuridine, agents that introduce base excision repair (BER) DNA substrates/intermediates.
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA.
authors.forename: Heng-Kuan
authors.initials: HK
authors.lastname: Wong
authors.forename: Meltem
authors.initials: M
authors.lastname: Muftuoglu
authors.forename: Gad
authors.initials: G
authors.lastname: Beck
authors.forename: Syed Z
authors.initials: SZ
authors.lastname: Imam
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.forename: David M
authors.initials: DM
authors.lastname: Wilson
mesh_terms: D002461:Cell Line, Transformed; D004265:DNA Helicases / Q000378:metabolism* / Q000502:physiology; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000378:metabolism* / Q000502:physiology; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism*; D015894:Genome, Human; D006801:Humans; D008741:Methyl Methanesulfonate / Q000633:toxicity; D000075223:Poly-ADP-Ribose Binding Proteins; D013936:Thymidine / Q000031:analogs & derivatives / Q000633:toxicity
chemical_list: D000075223:Poly-ADP-Ribose Binding Proteins; C018080:5-hydroxymethyl-2'-deoxyuridine; D008741:Methyl Methanesulfonate; D004265:DNA Helicases; C078673:ERCC6 protein, human; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D045643:DNA Repair Enzymes; D013936:Thymidine