title: Identification of two independent nucleosome-binding domains in the transcriptional co-activator SPBP.
abstract: Transcriptional regulation requires co-ordinated action of transcription factors, co-activator complexes and general transcription factors to access specific loci in the dense chromatin structure. In the present study we demonstrate that the transcriptional co-regulator SPBP [stromelysin-1 PDGF (platelet-derived growth factor)-responsive element binding protein] contains two independent chromatin-binding domains, the SPBP-(1551-1666) region and the C-terminal extended PHD [ePHD/ADD (extended plant homeodomain/ATRX-DNMT3-DNMT3L)] domain. The region 1551-1666 is a novel core nucleosome-interaction domain located adjacent to the AT-hook motif in the DNA-binding domain. This novel nucleosome-binding region is critically important for proper localization of SPBP in the cell nucleus. The ePHD/ADD domain associates with nucleosomes in a histone tail-dependent manner, and has significant impact on the dynamic interaction between SPBP and chromatin. Furthermore, SPBP and its homologue RAI1 (retinoic-acid-inducible protein 1), are strongly enriched on chromatin in interphase HeLa cells, and both proteins display low nuclear mobility. RAI1 contains a region with homology to the novel nucleosome-binding region SPBP-(1551-1666) and an ePHD/ADD domain with ability to bind nucleosomes. These results indicate that the transcriptional co-regulator SPBP and its homologue RAI1 implicated in Smith-Magenis syndrome and Potocki-Lupski syndrome both belong to the expanding family of chromatin-binding proteins containing several domains involved in specific chromatin interactions.
authors.affiliation: Molecular Cancer Research Group, Department of Medical Biology, University of Tromsø, 9037 Tromsø, Norway.
authors.forename: Sagar
authors.initials: S
authors.lastname: Darvekar
authors.forename: Sylvia Sagen
authors.initials: SS
authors.lastname: Johnsen
authors.forename: Agnete Bratsberg
authors.initials: AB
authors.lastname: Eriksen
authors.forename: Terje
authors.initials: T
authors.lastname: Johansen
authors.forename: Eva
authors.initials: E
authors.lastname: Sjøttem
mesh_terms: D002843:Chromatin / Q000378:metabolism; D022041:Euchromatin / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D009707:Nucleosomes / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D058496:Smith-Magenis Syndrome; D015534:Trans-Activators; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D002843:Chromatin; D022041:Euchromatin; D009707:Nucleosomes; C431552:RAI1 protein, human; C114750:TCF20 protein, human; D015534:Trans-Activators; D014157:Transcription Factors