title: SUMOylation of the transcriptional co-repressor KAP1 is regulated by the serine and threonine phosphatase PP1.
abstract: Krüppel-associated box (KRAB) domain-associated protein 1 [KAP1, also known as transcription intermediary factor-1beta (TIF1beta)] is a ubiquitous transcriptional co-repressor that is susceptible to phosphorylation at Ser(824) by ataxia-telangiectasia mutated (ATM) and to modification by small ubiquitin-like modifying (SUMO) proteins. Here, we found that, whereas the protein phosphatase 1alpha isoform (PP1alpha) directly interacted with KAP1 under basal conditions, PP1beta interacted with KAP1 only in response to genotoxic stress. Changes in the abundance of PP1alpha or PP1beta had differential effects on the phosphorylation and SUMOylation states of KAP1 under basal conditions and in response to DNA double-strand breaks (DSBs). Chromatin immunoprecipitation and re-immunoprecipitation experiments revealed that PP1alpha and PP1beta were recruited to KAP1 with different kinetics before and after the induction of DNA DSBs, which provided a mechanistic basis for the switch in the phosphorylation and SUMOylation states of KAP1. PP1beta-dependent SUMOylation of KAP1 occurred by mechanisms that were dependent and independent of the phosphorylation status of Ser(824). We posit a mechanism whereby the combined actions of PP1alpha and PP1beta cause dephosphorylation of KAP1 at Ser(824) and assure its SUMOylation to counter the effect of ATM, thereby regulating the transcription of KAP1 target genes in unstressed and stressed cells.
authors.affiliation: Department of Molecular Pharmacology, City of Hope Beckman Research Institute, Duarte, CA 91010, USA.
authors.forename: Xu
authors.initials: X
authors.lastname: Li
authors.forename: H Helen
authors.initials: HH
authors.lastname: Lin
authors.forename: Hanqing
authors.initials: H
authors.lastname: Chen
authors.forename: Xingzhi
authors.initials: X
authors.lastname: Xu
authors.forename: Hsiu-Ming
authors.initials: HM
authors.lastname: Shih
authors.forename: David K
authors.initials: DK
authors.lastname: Ann
mesh_terms: D001665:Binding Sites; D002453:Cell Cycle; D045744:Cell Line, Tumor; D004249:DNA Damage; D055785:Gene Knockdown Techniques; D006801:Humans; D047468:Immunoprecipitation; D007700:Kinetics; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D000076183:Tripartite Motif-Containing Protein 28
chemical_list: D012097:Repressor Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28; D010749:Phosphoprotein Phosphatases