Nuclear coactivator-62 kDa/Ski-interacting protein is a nuclear matrix-associated coactivator that may couple vitamin D receptor-mediated transcription and RNA splicing
Department of Cell Biology; Graduate School of Biomedical Sciences
Medical Subject Headings
Animals; Base Sequence; COS Cells; Calcitriol; Cell Nucleus; Cercopithecus aethiops; DNA Primers; Hela Cells; Humans; Nuclear Proteins; Plasmids; *RNA Splicing; RNA, Messenger; Receptors, Calcitriol; Recombinant Fusion Proteins; Reverse Transcriptase Polymerase Chain Reaction; Trans-Activators; Transcription Factors; *Transcription, Genetic; Transfection
Life Sciences | Medicine and Health Sciences
Nuclear coactivator-62 kDa/Ski-interacting protein (NCoA62/SKIP) is a putative vitamin D receptor (VDR) and nuclear receptor coactivator protein that is unrelated to other VDR coactivators such as those in the steroid receptor coactivator (SRC) family. The mechanism through which NCoA62/SKIP functions in VDR-activated transcription is unknown. In the present study, we identified a nuclear localization sequence in the COOH terminus of NCoA62/SKIP and showed that NCoA62/SKIP was targeted to nuclear matrix subdomains. Chromatin immunoprecipitation studies revealed that endogenous NCoA62/SKIP associated in a 1,25-dihydroxyvitamin D3-dependent manner with VDR target genes in ROS17/2.8 osteosarcoma cells. A cyclic pattern of promoter occupancy by VDR, SRC-1, and NCoA62/SKIP was observed, with NCoA62/SKIP entering these promoter complexes after SRC-1. These studies provide strong support for the proposed role of NCoA62/SKIP as a VDR transcriptional coactivator, and they indicate that key mechanistic differences probably exist between NCoA62/SKIP and SRC coactivators. To explore potential mechanisms, NCoA62/SKIP-interacting proteins were purified from HeLa cell nuclear extracts and identified by mass spectrometry. The identified proteins represent components of the spliceosome as well as other nuclear matrix-associated proteins. Here, we show that a dominant negative inhibitor of NCoA62/SKIP (dnNCoA62/SKIP) interfered with appropriate splicing of transcripts derived from 1,25-dihydroxyvitamin D3-induced expression of a growth hormone minigene cassette. Taken together, these data show that NCoA62/SKIP has properties that are consistent with those of nuclear receptor coactivators and with RNA spliceosome components, thus suggesting a potential role for NCoA62/SKIP in coupling VDR-mediated transcription to RNA splicing.
Rights and Permissions
Citation: J Biol Chem. 2003 Sep 12;278(37):35325-36. Epub 2003 Jul 2. Link to article on publisher's site