The maternally expressed Drosophila gene encoding the chromatin-binding protein BJ1 is a homolog of the vertebrate gene Regulator of Chromatin Condensation, RCC1

Max-Planck-Institut für Entwicklungsbiologie, Tübingen, FRG.
The EMBO Journal (Impact Factor: 10.43). 06/1991; 10(5):1225-36.
Source: PubMed


Using monoclonal antibodies I have identified a nuclear protein of Drosophila, BJ1 (Mr approximately 68 kd), and isolated its gene. Biochemical analysis demonstrates that the BJ1 protein is associated with nucleosomes and is released from chromatin by agents which intercalate into DNA, as previously shown for the high mobility group proteins (HMGs). On polytene chromosomes the protein is localized in all bands, with no preference for particular loci. Both the BJ1 protein and in particular the BJ1 mRNA are strongly expressed maternally. In early embryos all nuclei contain equal amounts of BJ1. During neuroblast formation, BJ1 mRNA becomes restricted to cells of the central nervous system, and higher protein levels are found in the nuclei of this tissue. In late embryonic stages, the mRNA almost completely disappears, but significant amounts of BJ1 protein persist until morphogenesis. The BJ1 gene encodes a 547 amino acid polypeptide featuring two different types of internal repeats. The sequence from amino acids 46 to 417 containing seven repeats of the first type has been highly conserved in evolution. 45% of the amino acids in this region are conserved in seven similar tandem repeats of the human gene Regulator of Chromatin Condensation, RCC1. The phenotype of a cell line carrying a mutation of RCC1 suggested a main function for this gene in cell cycle control. A yeast gene, SRM1/PRP20, also contains these repeats and shows 30% amino acid identity to BJ1 in this region. Mutations in this gene perturb mRNA metabolism, disrupt nuclear structure and alter the signal transduction pathway for the mating pheromone. Complementation experiments argue for a common function of these genes in the different species. I propose that their gene products bind to the chromatin to establish or maintain a proper higher order structure as a prerequisite for a regulated gene expression. Disruption of this structure could cause both mis-expression and default repression of genes, which might explain the pleiotropic phenotypes of the mutants.

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    • "Furthermore, it was shown that overexpression of Prp20p, which increases the transient concentration of nucleotide-free Gsp1p, specifically weakens telomeric silencing in a nucleocytoplasmic transport independent way (Clement et al., 2006). Prp20p is an essential and ubiquitous eukaryotic protein, and its homologs in mammals (Ohtsubo et al., 1987) and Xenopus laevis (Nishitani et al., 1990) were named as RCC1, while the homologs in Drosophila melanogaster (Frasch, 1991) and Schizosaccharomyces pombe (Matsumoto and Beach, 1991) were known as Bj1 and Pim1, respectively. They were proved to be functionally conserved in eukaryotes (Clark et al., 1991; Fleischmann et al., 1991; Nishitani et al., 1991; Ohtsubo et al., 1991). "
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    ABSTRACT: Prp20p is the homolog of mammalian RCC1 (regulator of chromosome condensation 1) in Saccharomyces cerevisiae, which acts as the guanine nucleotide exchange factor (GEF) for Gsp1p (yeast Ran). Prp20p plays multiple roles in mRNA metabolism, nucleocytoplasmic transport and mitosis regulation. Prp20p also functions as a linker between chromatin and nuclear pore complex (NPC) which regulates the NPC-mediated boundary activity (BA). Prp20p contains an N-terminal nuclear localization signal (NLS) and a typical RCC1-like domain (RLD). Here we present the 1.9Å crystal structure of the RCC1-like domain of Prp20p, which exhibits a classical seven-bladed β-propeller. We also proved that the additional β-wedge in Prp20p is essential for the interaction between Prp20p and Gsp1p. Based on this structure, we built a complex model of Prp20p and Gsp1p which was optimized by molecular dynamics (MD) simulations. Our model reveals that Prp20p and RCC1 share similar Ran GTPase binding mode. In addition, we also studied the histone-binding property of Prp20p in vitro.
    Full-text · Article · Nov 2010 · Journal of Structural Biology
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    • "During Drosophila development Bj1 (dRCC1) shows an expression profile similar to jumu. The gene is strongly maternally expressed and in embryos Bj1 is accumulated in cells of the central nervous system (Frasch 1991; Shi and Skeath 2004), and like jumu, the gene is required for eye and wing development (Shi and Skeath 2004). Following overexpression of jumu we observe a strong increase in anti-Bj1 antibody staining of polytene chromosomes (Supplementary Fig. 3). "
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    ABSTRACT: The PEV-modifying winged-helix/forkhead domain transcription factor JUMU of Drosophila is an essential protein of pleiotropic function. The correct gene dose of jumu is required for nucleolar integrity and correct nucleolus function. Overexpression of jumu results in bloating of euchromatic chromosome arms, displacement of the JUMU protein from the chromocenter and the nucleolus, fragile weak points, and disrupted chromocenter of polytene chromosomes. Overexpression of the acidic C terminus of JUMU alone causes nucleolus disorganization. In addition, euchromatic genes are overexpressed and HP1, which normally accumulates in the pericentric heterochromatin and spreads into euchromatic chromosome arms, although H3-K9 di-methylation remains restricted to the pericentric heterochromatin. The human winged-helix nude gene shows similarities to jumu and its overexpression in Drosophila causes bristle mutations.
    Full-text · Article · Mar 2010 · Chromosome Research
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    • "Of relevance to our studies is the observation that the addition of RCC1 or an activated form of Ran (Ran G19V ) stimulated microtubule assembly in the absence of chromatin (Kalab et al. 1999). Drosophila RCC1, a Ran cofactor, is found in the oocyte nucleus before and after NEB (Frasch 1991; this work) and Ran has also been suggested to have a role in meiotic spindle assembly in mouse oocytes (Cao et al. 2005) although there is evidence for RanGTP-independent pathways as well (Dumont et al. 2007). We are currently investigating if Ran signaling is involved in meiotic spindle assembly of Drosophila oocytes and if it is responsible for cytoplasmic state permissive to spindle assembly or the ''organizational field'' around the chromosomes or both. "
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    ABSTRACT: Bipolar spindles assemble in the absence of centrosomes in the oocytes of many species. In Drosophila melanogaster oocytes, the chromosomes have been proposed to initiate spindle assembly by nucleating or capturing microtubules, although the mechanism is not understood. An important contributor to this process is Subito, which is a kinesin-6 protein that is required for bundling interpolar microtubules located within the central spindle at metaphase I. We have characterized the domains of Subito that regulate its activity and its specificity for antiparallel microtubules. This analysis has revealed that the C-terminal domain may interact independently with microtubules while the motor domain is required for maintaining the interaction with the antiparallel microtubules. Surprisingly, deletion of the N-terminal domain resulted in a Subito protein capable of promoting the assembly of bipolar spindles that do not include centrosomes or chromosomes. Bipolar acentrosomal spindle formation during meiosis in oocytes may be driven by the bundling of antiparallel microtubules. Furthermore, these experiments have revealed evidence of a nuclear- or chromosome-based signal that acts at a distance to activate Subito. Instead of the chromosomes directly capturing microtubules, signals released upon nuclear envelope breakdown may activate proteins like Subito, which in turn bundles together microtubules.
    Preview · Article · Oct 2007 · Genetics
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