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Query: UMLS:C0393754 (HSA)
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ATP-dependent nucleosome remodeling plays a central role in the regulation of access to chromatin DNA. Swi/Snf remodeling complexes characterized in yeast, Drosophila and mammals all contain a conserved set of core subunits composed of homologs of yeast SNF2-type DNA-dependent ATPase, SNF5 and SWI3 proteins. So far, no complete Swi/Snf-type complex has been characterized in plants. Arabidopsis contains a single SNF5-type gene, BSH, which has been shown to complement the yeast snf5 mutation. Here we describe the characterization of AtSWI3B, the smallest of the four Arabidopsis homologs of SWI3. The gene encoding AtSWI3B is expressed ubiquitously in the plant. AtSWI3B is localized to nuclei and is associated mostly with the chromatin and soluble protein fractions. When expressed in Saccharomyces cerevisiae, the cDNA encoding AtSWI3B partially complements the swi3 mutant phenotype. However, like BSH, AtSWI3B is unable to activate transcription in yeast when tethered to DNA. The analysis by yeast two-hybrid indicates that AtSWI3B is capable of forming homodimers and interacts with BSH as well as with two other members of the Arabidopsis SWI3 family: AtSWI3A and AtSWI3C. The results of phage display screen using recombinant protein, confirmed by direct yeast two-hybrid analyses, indicate that AtSWI3B interacts with FCA, a regulator of flowering time in Arabidopsis. This interaction is through the C-terminal region of FCA, located outside the conserved RNA- and protein-binding domains of this protein.
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PMID:AtSWI3B, an Arabidopsis homolog of SWI3, a core subunit of yeast Swi/Snf chromatin remodeling complex, interacts with FCA, a regulator of flowering time. 1214 Mar 26

SWITCH/SUCROSE NONFERMENTING (SWI/SNF) chromatin-remodeling complexes mediate ATP-dependent alterations of DNA-histone contacts. The minimal functional core of conserved SWI/SNF complexes consists of a SWI2/SNF2 ATPase, SNF5, SWP73, and a pair of SWI3 subunits. Because of early duplication of the SWI3 gene family in plants, Arabidopsis thaliana encodes four SWI3-like proteins that show remarkable functional diversification. Whereas ATSWI3A and ATSWI3B form homodimers and heterodimers and interact with BSH/SNF5, ATSWI3C, and the flowering regulator FCA, ATSWI3D can only bind ATSWI3B in yeast two-hybrid assays. Mutations of ATSWI3A and ATSWI3B arrest embryo development at the globular stage. By a possible imprinting effect, the atswi3b mutations result in death for approximately half of both macrospores and microspores. Mutations in ATSWI3C cause semidwarf stature, inhibition of root elongation, leaf curling, aberrant stamen development, and reduced fertility. Plants carrying atswi3d mutations display severe dwarfism, alterations in the number and development of flower organs, and complete male and female sterility. These data indicate that, by possible contribution to the combinatorial assembly of different SWI/SNF complexes, the ATSWI3 proteins perform nonredundant regulatory functions that affect embryogenesis and both the vegetative and reproductive phases of plant development.
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PMID:SWI3 subunits of putative SWI/SNF chromatin-remodeling complexes play distinct roles during Arabidopsis development. 1605 36