title: HMGB1 Stimulates Activity of Polymerase β on Nucleosome Substrates.
abstract: The process of base excision repair (BER) recognizes and repairs small lesions or inappropriate bases on DNA through either a short-patch or long-patch pathway. The enzymes involved in BER have been well-characterized on DNA substrates, and, somewhat surprisingly, many of these enzymes, including several DNA glycosylases, AP endonuclease (APE), FEN1 endonuclease, and DNA ligases, have been shown to have activity on DNA substrates within nucleosomes. DNA polymerase β (Pol β), however, exhibits drastically reduced or no activity on nucleosomal DNA. Interestingly, acetylation of Pol β, by the acetyltransferase p300, inhibits its 5' dRP-lyase activity and presumably pushes repair of DNA substrates through the long-patch base excision repair (LP-BER) pathway. In addition to the major enzymes involved in BER, a chromatin architectural factor, HMGB1, was found to directly interact with and enhance the activity of APE1 and FEN1, and thus may aid in altering the structure of the nucleosome to be more accessible to BER factors. In this work, we investigated whether acetylation of Pol β, either alone or in conjunction with HMGB1, facilitates its activity on nucleosome substrates. We find acetylated Pol β exhibits enhanced strand displacement synthesis activity on DNA substrates, but, similar to the unmodified enzyme, has little or no activity on nucleosomes. Preincubation of DNA templates with HMGB1 has little or no stimulatory effect on Pol β and even is inhibitory at higher concentrations. In contrast, preincubation of nucleosomes with HMGB1 rescues Pol β gap-filling activity in nucleosomes, suggesting that this factor may help overcome the repressive effects of chromatin.
authors.affiliation: Department of Biochemistry & Biophysics, University of Rochester Medical Center , Rochester, New York 14642, United States.
authors.forename: Angela
authors.initials: A
authors.lastname: Balliano
authors.affiliation: Department of Biochemistry & Biophysics, University of Rochester Medical Center , Rochester, New York 14642, United States.|Department of Biology, Indiana University Purdue University Indianapolis , 723 W. Michigan Street, Indianapolis, Indiana 46202-5132, United States.
authors.forename: Fanfan
authors.initials: F
authors.lastname: Hao
authors.affiliation: Department of Biology, Indiana University Purdue University Indianapolis , 723 W. Michigan Street, Indianapolis, Indiana 46202-5132, United States.
authors.forename: Catherine
authors.initials: C
authors.lastname: Njeri
authors.affiliation: Department of Biology, Indiana University Purdue University Indianapolis , 723 W. Michigan Street, Indianapolis, Indiana 46202-5132, United States.
authors.forename: Lata
authors.initials: L
authors.lastname: Balakrishnan
authors.affiliation: Department of Biochemistry & Biophysics, University of Rochester Medical Center , Rochester, New York 14642, United States.
authors.forename: Jeffrey J
authors.identifier: 0000-0001-6981-1803
authors.initials: JJ
authors.lastname: Hayes
mesh_terms: D000107:Acetylation; D000818:Animals; D002645:Chickens; D004247:DNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019951:DNA Polymerase beta / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D015870:Gene Expression; D024243:HMGB1 Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006657:Histones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D009707:Nucleosomes / Q000378:metabolism* / Q000648:ultrastructure; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D014981:Xenopus; D050880:p300-CBP Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000099224:p300-CBP-Associated Factor
chemical_list: D004247:DNA; D019951:DNA Polymerase beta; D024243:HMGB1 Protein; D006657:Histones; D009707:Nucleosomes; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C585491:HMGB1 protein, human