The transcriptional co-repressor C-terminal binding protein (CtBP) associates with centrosomes during mitosis.
CtBP is a corepressor of transcription that acts by inhibiting coactivators and recruiting to promoter control elements (via interactions with DNA-binding transcription factors) a complex of proteins that modify histones, repress transcription and silence gene expression. There are two highly homologous genes, CtBP1 and CtBP2 that encode CtBP. In addition, a CtBP1-related protein has been described that has 11 fewer amino acids at its N-terminus than CtBP1. This variant of CtBP1--known as CtBP3 or BARS [Brefeldin A (BFA) ribosylated substrate]--plays a critical role in the fragmentation of the Golgi complex at the onset of mitosis. Although there are some reports of CtBP with a cytoplasmic distribution after transfection, it is unclear how in normal cells a nuclear corepressor regulates the behavior of the Golgi complex at the onset of mitosis. Using polyclonal rabbit antibodies that were raised against a human CtBP1-GST fusion-protein, here we show by immunofluorescence laser-scanning confocal microscopy that in mitotic cells a species of CtBP becomes associated with the centrosomes at the onset of prophase and then throughout mitosis. The association can be seen in both cycling mitotic cells and nocodazole-arrested cells. The interaction was confirmed by coimmunoprecipitation and centrosome isolation. Since centrosomes are considered to be the organising centre for Golgi morphogenesis, the interaction demonstrated here may explain how a nuclear corepressor of transcription can exert a regulatory effect on the Golgi complex at a specific stage of the cell cycle.
Spyer
Moira
M
Department of Virology, Faculty of Medicine, Imperial College London, Norfolk Place, London, UK.
Allday
Martin J
MJ
D000429:Alcohol Oxidoreductases; D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D018385:Centrosome / Q000187:drug effects / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D007399:Interphase; D008938:Mitosis / Q000187:drug effects / Q000502:physiology*; D015739:Nocodazole / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D015203:Reproducibility of Results; D014158:Transcription, Genetic; D014404:Tubulin / Q000378:metabolism; D000097869:Polo-Like Kinase 1
D000429:Alcohol Oxidoreductases; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D015739:Nocodazole; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014404:Tubulin; D000097869:Polo-Like Kinase 1; C096794:C-terminal binding protein