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WSTF-ISWI chromatin remodeling complex targets heterochromatic replication foci.

ABSTRACT: The Williams Syndrome Transcription Factor (WSTF), the product of the WBSCR9 gene, is invariably deleted in the haploinsufficiency Williams-Beuren Syndrome. Along with the nucleosome-dependent ATPase ISWI, WSTF forms a novel chromatin remodeling complex, WICH (WSTF-ISWI chromatin remodeling complex), which is conserved in vertebrates. The WICH complex was purified to homogeneity from Xenopus egg extract and was found to contain only WSTF and ISWI. In mouse cells, WSTF interacts with the SNF2H isoform of ISWI. WSTF accumulates in pericentric heterochromatin coincident with the replication of these structures, suggesting a role for WSTF in the replication of heterochromatin. Such a role is supported by the in vitro activity of both the mouse and frog WICH complexes: they are involved in the assembly of regular spaced nucleosomal arrays. In contrast to the related ISWI-interacting protein ACF1/WCRF180, WSTF binds stably to mitotic chromosomes. As dysfunction of other chromatin remodeling factors often has severe effects on development, haploinsufficiency of WSTF may explain some of the phenotypes associated with this disease.

SUBMITTER: Bozhenok L

PROVIDER: S-EPMC125993 | biostudies-literature | 2002 May

REPOSITORIES: biostudies-literature

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WSTF-ISWI chromatin remodeling complex targets heterochromatic replication foci.

Bozhenok Ludmila L Wade Paul A PA Varga-Weisz Patrick P

The EMBO journal 20020501 9

The Williams Syndrome Transcription Factor (WSTF), the product of the WBSCR9 gene, is invariably deleted in the haploinsufficiency Williams-Beuren Syndrome. Along with the nucleosome-dependent ATPase ISWI, WSTF forms a novel chromatin remodeling complex, WICH (WSTF-ISWI chromatin remodeling complex), which is conserved in vertebrates. The WICH complex was purified to homogeneity from Xenopus egg extract and was found to contain only WSTF and ISWI. In mouse cells, WSTF interacts with the SNF2H is ...[more]

PMID: 11980720

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Project description:Wongabel virus (WONV) is an arthropod-borne rhabdovirus that infects birds. It is one of the growing array of rhabdoviruses with complex genomes that encode multiple accessory proteins of unknown function. In addition to the five canonical rhabdovirus structural protein genes (N, P, M, G, and L), the 13.2-kb negative-sense single-stranded RNA (ssRNA) WONV genome contains five uncharacterized accessory genes, one overlapping the N gene (Nx or U4), three located between the P and M genes (U1 to U3), and a fifth one overlapping the G gene (Gx or U5). Here we show that WONV U3 is expressed during infection in insect and mammalian cells and is required for efficient viral replication. A yeast two-hybrid screen against a mosquito cell cDNA library identified that WONV U3 interacts with the 83-amino-acid (aa) C-terminal domain of SNF5, a component of the SWI/SNF chromatin remodeling complex. The interaction was confirmed by affinity chromatography, and nuclear colocalization was established by confocal microscopy. Gene expression studies showed that SNF5 transcripts are upregulated during infection of mosquito cells with WONV, as well as West Nile virus (Flaviviridae) and bovine ephemeral fever virus (Rhabdoviridae), and that SNF5 knockdown results in increased WONV replication. WONV U3 also inhibits SNF5-regulated expression of the cytokine gene CSF1. The data suggest that WONV U3 targets the SWI/SNF complex to block the host response to infection.The rhabdoviruses comprise a large family of RNA viruses infecting plants, vertebrates, and invertebrates. In addition to the major structural proteins (N, P, M, G, and L), many rhabdoviruses encode a diverse array of accessory proteins of largely unknown function. Understanding the role of these proteins may reveal much about host-pathogen interactions in infected cells. Here we examine accessory protein U3 of Wongabel virus, an arthropod-borne rhabdovirus that infects birds. We show that U3 enters the nucleus and interacts with SNF5, a component of the chromatin remodeling complex that is upregulated in response to infection and restricts viral replication. We also show that U3 inhibits SNF5-regulated expression of the cytokine colony-stimulating factor 1 (CSF1), suggesting that it targets the chromatin remodeling complex to block the host response to infection. This study appears to provide the first evidence of a virus targeting SNF5 to inhibit host gene expression.

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WSTF-ISWI chromatin remodeling complex targets heterochromatic replication foci.

Publications

WSTF-ISWI chromatin remodeling complex targets heterochromatic replication foci.

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