title: Phosphorylation of linker histones by DNA-dependent protein kinase is required for DNA ligase IV-dependent ligation in the presence of histone H1.
abstract: DNA nonhomologous end-joining in vivo requires the DNA-dependent protein kinase (DNA-PK) and DNA ligase IV/XRCC4 (LX) complexes. Here, we have examined the impact of histone octamers and linker histone H1 on DNA end-joining in vitro. Packing of the DNA substrate into dinucleosomes does not significantly inhibit ligation by LX. However, LX ligation activity is substantially reduced by the incorporation of linker histones. This inhibition is independent of the presence of core histone octamers and cannot be restored by addition of Ku alone but can be partially rescued by DNA-PK. The kinase activity of DNA-PK is essential for the recovery of end-joining. DNA-PK efficiently phosphorylates histone H1. Phosphorylated histone H1 has a reduced affinity for DNA and a decreased capacity to inhibit end-joining. Our findings raise the possibility that DNA-PK may act as a linker histone kinase by phosphorylating linker histones in the vicinity of a DNA break and coupling localized histone H1 release from DNA ends, with the recruitment of LX to carry out double-stranded ligation. Thus, by using histone H1-bound DNA as a template, we have reconstituted the end-joining step of DNA nonhomologous end-joining in vitro with a requirement for DNA-PK.
authors.affiliation: Genome Damage and Stability Center, University of Sussex, Brighton BN1 9RQ, United Kingdom.
authors.forename: Boris
authors.initials: B
authors.lastname: Kysela
authors.forename: Miroslav
authors.initials: M
authors.lastname: Chovanec
authors.forename: Penny A
authors.initials: PA
authors.lastname: Jeggo
mesh_terms: D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism*; D006801:Humans; D000072200:Ku Autoantigen; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D009707:Nucleosomes / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D006657:Histones; C000607893:LIG4 protein, human; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D009707:Nucleosomes; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D011088:DNA Ligases; D000072481:DNA Ligase ATP