title: Structural insights into human KAP1 PHD finger-bromodomain and its role in gene silencing.
abstract: The tandem PHD finger-bromodomain, found in many chromatin-associated proteins, has an important role in gene silencing by the human co-repressor KRAB-associated protein 1 (KAP1). Here we report the three-dimensional solution structure of the tandem PHD finger-bromodomain of KAP1. The structure reveals a distinct scaffold unifying the two protein modules, in which the first helix, alpha(Z), of an atypical bromodomain forms the central hydrophobic core that anchors the other three helices of the bromodomain on one side and the zinc binding PHD finger on the other. A comprehensive mutation-based structure-function analysis correlating transcriptional repression, ubiquitin-conjugating enzyme 9 (UBC9) binding and SUMOylation shows that the PHD finger and the bromodomain of KAP1 cooperate as one functional unit to facilitate lysine SUMOylation, which is required for KAP1 co-repressor activity in gene silencing. These results demonstrate a previously unknown unified function for the tandem PHD finger-bromodomain as an intramolecular small ubiquitin-like modifier (SUMO) E3 ligase for transcriptional silencing.
authors.affiliation: Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York University, 1425 Madison Avenue, New York, New York 10029, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Zeng
authors.forename: Kyoko L
authors.initials: KL
authors.lastname: Yap
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Ivanov
authors.forename: Xueqi
authors.initials: X
authors.lastname: Wang
authors.forename: Shiraz
authors.initials: S
authors.lastname: Mujtaba
authors.forename: Olga
authors.initials: O
authors.lastname: Plotnikova
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Rauscher
authors.forename: Ming-Ming
authors.initials: MM
authors.lastname: Zhou
mesh_terms: D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology*; D015536:Down-Regulation; D020868:Gene Silencing; D006801:Humans; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000502:physiology*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism; D012996:Solutions; D014158:Transcription, Genetic; D000076183:Tripartite Motif-Containing Protein 28; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases; D016335:Zinc Fingers; D000098843:Ubiquitin-Conjugating Enzyme UBC9
chemical_list: D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; D012996:Solutions; D044763:Ubiquitin-Conjugating Enzymes; C101116:TRIM28 protein, human; D000076183:Tripartite Motif-Containing Protein 28; D044767:Ubiquitin-Protein Ligases; D000098843:Ubiquitin-Conjugating Enzyme UBC9