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J. Biol. Chem., Vol. 283, Issue 2, 940-950, January 11, 2008
Isolation of XAB2 Complex Involved in Pre-mRNA Splicing, Transcription, and Transcription-coupled Repair*![]() 1![]() ![]() 2![]() ![]() 3![]() ![]() ![]() 4
From the
Nucleotide excision repair is a versatile repair pathway that counteracts the deleterious effects of various DNA lesions. In nucleotide excision repair, there is a transcription-coupled repair (TCR) pathway that focuses on DNA damage that blocks RNA polymerase IIo in transcription elongation. XAB2 (XPA-binding protein 2), containing tetratricopeptide repeats, has been isolated by virtue of its ability to interact with xeroderma pigmentosum group A protein (XPA). Moreover, XAB2 has been shown to interact with Cockayne syndrome group A and B proteins (CSA and CSB) and RNA polymerase II, as well as XPA, and is involved in TCR and transcription. Here we purified XAB2 as a multimeric protein complex consisting of hAquarius, XAB2, hPRP19, CCDC16, hISY1, and PPIE, which are involved in pre-mRNA splicing. Knockdown of XAB2 with small interfering RNA in HeLa cells resulted in a hypersensitivity to killing by UV light and a decreased recovery of RNA synthesis after UV irradiation and regular RNA synthesis. Enhanced interaction of XAB2 with RNA polymerase IIo or XPA was observed in cells treated with DNA-damaging agents, indicating DNA damage-responsive activity of the XAB2 complex. These results indicated that the XAB2 complex is a multifunctional factor involved in pre-mRNA splicing, transcription, and TCR.
Received for publication, August 10, 2007 , and in revised form, October 29, 2007. * This work was supported in part by a grant-in-aid for scientific research from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and Solution-oriented Research for Science and Technology of Japan Science and Technology Corp. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 2 Recipient of an Advanced Biotechnology Scholarship from Ishihara Sangyo Kaisha, Ltd., in collaboration with the Singapore Economic Development Board. 3 Present address: Dept. of Medical Biophysics and Radiation Biology, Graduate School of Medical Science, Kyushu University, Fukuoka 812-8582, Japan. 1 To whom correspondence may be addressed. Tel.: 81-92-541-3231; Fax: 81-92-542-8534; E-mail: ikuraoka{at}nk-cc.go.jp. 4 To whom correspondence may be addressed. Tel.: 81-6-6879-7971; Fax: 81-6-6877-9136; E-mail: ktanaka{at}fbs.osaka-u.ac.jp.
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