XAB2, a novel tetratricopeptide repeat protein involved in transcription-coupled DNA repair and transcription

Nucleotide excision repair is a highly versatile DNA repair system responsi ble for elimination of a wide variety of lesions from the genome. It is com prised of two subpathways: transcription-coupled repair that accomplishes e fficient removal of damage blocking transcription and global genome repair, Recently, the basic mechanism of global genome repair has emerged from bio chemical studies. However, little is known about transcription-coupled repa ir in eukaryotes, Here we report the identification of a novel protein desi gnated XAB2 (XPA-binding protein 2) that was identified by virtue of its ab ility to interact with XPA, a factor central to both nucleotide excision re pair subpathways, The XAB2 protein of 855 amino acids consists mainly of 15 tetratricopeptide repeats. In addition to interacting with XPA, immunoprec ipitation experiments demonstrated that a fraction of XAB2 is able to inter act with the transcription-coupled repair-specific proteins CSA and CSB as well as RNA polymerase II. Furthermore, antibodies against XAB2 inhibited b oth transcription-coupled repair and transcription in vivo but not global g enome repair when microinjected into living fibroblasts. These results indi cate that XAB2 is a novel component involved in transcription-coupled repai r and transcription.