title: Histone H1 functions as a stimulatory factor in backup pathways of NHEJ.
abstract: DNA double-strand breaks (DSBs) induced in the genome of higher eukaryotes by ionizing radiation (IR) are predominantly removed by two pathways of non-homologous end-joining (NHEJ) termed D-NHEJ and B-NHEJ. While D-NHEJ depends on the activities of the DNA-dependent protein kinase (DNA-PK) and DNA ligase IV/XRCC4/XLF, B-NHEJ utilizes, at least partly, DNA ligase III/XRCC1 and PARP-1. Using in vitro end-joining assays and protein fractionation protocols similar to those previously applied for the characterization of DNA ligase III as an end-joining factor, we identify here histone H1 as an additional putative NHEJ factor. H1 strongly enhances DNA-end joining and shifts the product spectrum from circles to multimers. While H1 enhances the DNA-end-joining activities of both DNA Ligase IV and DNA Ligase III, the effect on ligase III is significantly stronger. Histone H1 also enhances the activity of PARP-1. Since histone H1 has been shown to counteract D-NHEJ, these observations and the known functions of the protein identify it as a putative alignment factor operating preferentially within B-NHEJ.
authors.affiliation: University of Duisburg-Essen, Medical School, Institute of Medical Radiation Biology, 45122 Essen, Germany.
authors.forename: Bustanur
authors.initials: B
authors.lastname: Rosidi
authors.forename: Minli
authors.initials: M
authors.lastname: Wang
authors.forename: Wenqi
authors.initials: W
authors.lastname: Wu
authors.forename: Aparna
authors.initials: A
authors.lastname: Sharma
authors.forename: Huichen
authors.initials: H
authors.lastname: Wang
authors.forename: George
authors.initials: G
authors.lastname: Iliakis
mesh_terms: D002457:Cell Extracts / Q000737:chemistry; D002467:Cell Nucleus / Q000737:chemistry; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D011088:DNA Ligases / Q000378:metabolism; D004260:DNA Repair; D006367:HeLa Cells; D006657:Histones / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D053719:Tandem Mass Spectrometry
chemical_list: D002457:Cell Extracts; D006657:Histones; D004247:DNA; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D011088:DNA Ligases