Microspherule protein 1, Mi-2beta, and RET finger protein associate in the nucleolus and up-regulate ribosomal gene transcription.

The nucleolus is the site of ribosomal DNA (rDNA) transcription and ribosome production. In exploring the role of nucleolar protein MCRS1 (microspherule protein1)/MSP58 (58-kDa microspherule protein), we found that Mi-2beta, a component of a nucleosome remodeling and deacetylase (NuRD) complex, RET finger protein (RFP), and upstream binding factor (UBF) were ...
associated with MCRS1. Yeast two-hybrid assays revealed that MCRS1 bound to the ATPase/helicase region of Mi-2beta and the coiled-coil region of RFP. Interestingly, confocal microscopic analyses revealed the co-localization of MCRS1, Mi-2beta, RFP, and the rRNA transcription factor UBF in the nucleoli. We also found that MCRS1, Mi-2beta, and RFP were associated with rDNA using a chromatin immunoprecipitation assay. Finally, we showed that MCRS1, Mi-2beta, and RFP up-regulated transcriptional activity of the rDNA promoter and that ribosomal RNA transcription was repressed when MCRS1, Mi-2beta, and RFP expression was reduced using siRNA. These results indicated that Mi-2beta and RFP, known to be involved in transcriptional repression in the nucleus, co-localize with MCRS1 in the nucleolus and appear to activate the rRNA transcription.
Mesh Terms:
Adenosine Triphosphatases, Autoantigens, Binding Sites, Cell Line, Cell Nucleolus, Chromatin Assembly and Disassembly, DNA Helicases, DNA, Ribosomal, DNA-Binding Proteins, Humans, Mi-2 Nucleosome Remodeling and Deacetylase Complex, Nuclear Proteins, Promoter Regions, Genetic, Protein Structure, Tertiary, RNA-Binding Proteins, Recombinant Proteins, Ribosomes, Two-Hybrid System Techniques, Up-Regulation
J. Biol. Chem.
Date: Nov. 25, 2005
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