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Molecular and Cellular Biology, April 2007, p. 2538-2547, Vol. 27, No. 7
0270-7306/07/$08.00+0 doi:10.1128/MCB.01288-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Graduate School of Frontier Biosciences, Osaka University,1 Solution Oriented Research for Science and Technology of Japan Science and Technology Agency, Yamadaoka 1-3, Suita, Osaka 565-0871, Japan2
Received 14 July 2006/ Returned for modification 6 September 2006/ Accepted 8 January 2007
Transcription-coupled repair (TCR) efficiently removes a variety of lesions from the transcribed strand of active genes. Mutations in Cockayne syndrome group A and B genes (CSA and CSB) result in defective TCR, but the molecular mechanism of TCR in mammalian cells is not clear. We have found that CSA protein is translocated to the nuclear matrix after UV irradiation and colocalized with the hyperphosphorylated form of RNA polymerase II and that the translocation is dependent on CSB. We developed a cell-free system for the UV-induced translocation of CSA. A cytoskeleton (CSK) buffer-soluble fraction containing CSA and a CSK buffer-insoluble fraction prepared from UV-irradiated CS-A cells were mixed. After incubation, the insoluble fraction was treated with DNase I. CSA protein was detected in the DNase I-insoluble fraction, indicating that it was translocated to the nuclear matrix. In this cell-free system, the translocation was dependent on UV irradiation, CSB function, and TCR-competent CSA. Moreover, the translocation was dependent on functional TFIIH, as well as chromatin structure and transcription elongation. These results suggest that alterations of chromatin at the RNA polymerase II stall site, which depend on CSB and TFIIH at least, are necessary for the UV-induced translocation of CSA to the nuclear matrix.
Published ahead of print on 22 January 2007.
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