Two related ARID family proteins are alternative subunits of human SWI/SNF complexes.

Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Biochemical Journal (Impact Factor: 4.78). 11/2004; 383(Pt 2):319-25. DOI: 10.1042/BJ20040524
Source: PubMed

ABSTRACT p270 (ARID1A) is a member of the ARID family of DNA-binding proteins and a subunit of human SWI/SNF-related complexes, which use the energy generated by an integral ATPase subunit to remodel chromatin. ARID1B is an independent gene product with an open reading frame that is more than 60% identical with p270. We have generated monoclonal antibodies specific for either p270 or ARID1B to facilitate the investigation of ARID1B and its potential interaction with human SWI/SNF complexes in vivo. Immunocomplex analysis provides direct evidence that endogenous ARID1B is associated with SWI/SNF-related complexes and indicates that p270 and ARID1B, similar to the ATPase subunits BRG1 and hBRM, are alternative, mutually exclusive subunits of the complexes. The ARID-containing subunits are not specific to the ATPases. Each associates with both BRG1 and hBRM, thus increasing the number of distinct subunit combinations known to be present in cells. Analysis of the panels of cell lines indicates that ARID1B, similar to p270, has a broad tissue distribution. The ratio of p270/ARID1B in typical cells is approx. 3.5:1, and BRG1 is distributed proportionally between the two ARID subunits. Analysis of DNA-binding behaviour indicates that ARID1B binds DNA in a non-sequence-specific manner similar to p270.

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    ABSTRACT: To explore the association between AT-rich interactive domain 1A (ARID1A) protein loss by immunohistochemistry and both clinicopathologic characteristics and prognosis in patients with colorectal cancer. We retrospectively collected clinicopathologic data and archived paraffin-embedded primary colorectal cancer samples from 209 patients, including 111 patients with colon cancer and 98 patients with rectal cancer. The tumor stage ranged from stage I to stage IV according to the 7(th) edition of the American Joint Committee on Cancer tumor-node-metastasis (TNM) staging system. All patients underwent resection of primary colorectal tumors. The expression of ARID1A protein in primary colorectal cancer tissues was examined by immunohistochemical staining. The clinicopathologic association and survival relevance of ARID1A protein loss in colorectal cancer were analyzed. ARID1A loss by immunohistochemistry was not rare in primary colorectal cancer tumors (25.8%). There were 7.4%, 24.1%, 22.2% and 46.3% of patients with ARID1A loss staged at TNM stage I, II, III and IV, respectively, compared with 20.0%, 22.6%, 27.7% and 29.7% of patients without ARID1A loss staged at TNM stage I, II, III and IV, respectively. In patients with ARID1A loss, the distant metastasis rate was 46.3%. However, only 29.7% of patients without ARID1A loss were found to have distant metastasis. In terms of pathologic differentiation, there were 25.9%, 66.7% and 7.4% with poorly, moderately and well differentiated tumors in patients with ARID1A loss, and 14.2%, 72.3% and 13.5% with poorly, moderately and well differentiated tumors in patients without ARID1A loss, respectively. ARID1A loss was associated with late TNM stage (P = 0.020), distant metastasis (P = 0.026), and poor pathological classification (P = 0.035). However, patients with positive ARID1A had worse overall survival compared to those with negative ARID1A in stage IV colorectal cancer (HR = 2.49, 95%CI: 1.13-5.51). ARID1A protein loss is associated with clinicopathologic characteristics in colorectal cancer patients and with survival in stage IV patients.
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    ABSTRACT: Mutations in the gene encoding AT-rich interactive domain-containing protein 1B (ARID1B) were recently associated with multiple syndromes characterized by developmental delay and intellectual disability, in addition to nonsyndromic intellectual disability. While the majority of ARID1B mutations identified to date are predicted to result in haploinsufficiency, the underlying pathogenic mechanisms have yet to be fully understood. ARID1B is a DNA-binding subunit of the Brahma-associated factor chromatin remodelling complexes, which play a key role in the regulation of gene activity. The function of remodelling complexes can be regulated by their subunit composition, and there is some evidence that ARID1B is a component of the neuron-specific chromatin remodelling complex. This complex is involved in the regulation of stem/progenitor cells exiting the cell cycle and differentiating into postmitotic neurons. Recent research has indicated that alterations in the cell cycle contribute to the underlying pathogenesis of syndromes associated with ARID1B haploinsufficiency in fibroblasts derived from affected individuals. This review describes studies linking ARID1B to neurodevelopmental disorders and it summarizes the function of ARID1B to provide insights into the pathogenic mechanisms underlying ARID1B-mediated disorders. In conclusion, ARID1B is likely to play a key role in neurodevelopment and reduced levels of wild-type protein compromise normal brain development. Additional studies are required to determine the mechanisms by which impaired neural development contributes to the intellectual disability and speech impairment that are consistently observed in individuals with ARID1B haploinsufficiency.
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