The 19S complex of the proteasome regulates nucleotide excision repair in yeast

Abstract

Nucleotide excision repair (NER) promotes the removal of various types of bulky base damage from DNA by a multistage process involving ∼30 different proteins (for review, see Friedberg et al. 1995). The majority of these proteins are highly conserved from yeast to man (for review, see Friedberg et al. 1995). Mutations in NER genes lead to hypersensitivity to killing as well as hypermutability following exposure to DNA-damaging agents such as ultraviolet (UV) radiation. Defective NER in humans predisposes to skin cancer following sunlight exposure, as exemplified by the hereditary NER-defective disease xeroderma pigmentosum (XP). The regulation of NER in living cells is therefore a question of both fundamental and clinical interest. In this study, we demonstrate novel functional relationships between NER and the proteasome in the yeast Saccharomyces cerevisiae.Rad23 protein is one of the multiple proteins involved in NER in S. cerevisiae (Friedberg et al. 1995). The precise function of this protein in this process is not clear.Extracts from cells deleted of the RAD23 gene do not support detectable NER in vitro (Wang et al. 1997;Russell et al. 1999). Such mutants, however, display a level of UV radiation sensitivity that is intermediate between that of wild-type strains and strains deleted for other RAD genes that are indispensable for NER, such as RAD1, RAD2, RAD3, etc. (Watkins et al. 1993;Mueller and Smerdon 1996). In some studies, this intermediate UV radiation sensitivity has been correlated with a partial decrease in NER in vivo (Mueller and Smerdon 1996).Human cells possess two homologs of the yeast RAD23 gene, designated HHR23A and HHR23B (Masutani et al. 1994). HHR23B protein binds tightly to human XPC protein and stimulates the rate of NER in vitro (Masutani et al. 1994(Masutani et al. , 1997Li et al. 1997). On the other hand, deletion of the mouse HHRAD23A or HHRAD23B genes does not result in increased sensitivity to UV radiation in mouse embryo fibroblasts (Friedberg and Meira 2000). Remarkably, mice deleted of the HHRAD23B gene show defective post-natal growth and HHRAD23A HHRAD23B double deletion mutants are inviable (Friedberg and Meira 2000). These observations suggest the existence of as yet unidentified essential functions of HHRAD23 protein, which is partially redundant between the A and B forms.Levels of human HHRAD23A protein are regulated in

Proteasome Activity Is Required for Androgen Receptor Transcriptional Activity via Regulation of Androgen Receptor Nuclear Translocation and Interaction with Coregulators in Prostate Cancer Cells

“…Accumulating evidence indicates that the proteasome not only plays a proteolytic role in protein degradation but also plays a non-proteolytic role in transcription elongation, nuclear excision repair, and protein trafficking (1,(37)(38)(39)(40)(41). Our results demonstrating that inhibition of proteasome function by MG132 attenuates androgen-induced AR nuclear translocation further support the non-proteolytic role of the proteasome in protein trafficking (1,37,38).…”

dDsk2 regulates H2Bub1 and RNA polymerase II pausing at dHP1c complex target genes

“…Ubiquitin receptors have been previously reported to play nonproteolytic functions in DNA repair and transcription elongation [6][7][8][9] . Furthermore, in response to DNA damage, human Rad23B was found to interact with ubiquitylated p53, localize at chromatin and accumulate at the p21 promoter 59 .…”

“…In addition, although generally poorly understood, ubiquitin receptors also play nonproteolytic functions (reviewed in refs 2,4,5). In particular, it was reported that Rad23 is required for optimal nucleotide excision repair (NER) in yeast and that this requirement involves nonproteolytic functions of the 19S regulatory complex (19S-RC) of the proteasome [6][7][8] . The 19S-RC has also been shown to play nonproteolytic functions in transcription elongation 9 .…”

The role of the ubiquitin/proteasome system in cellular responses to radiation

“…RAD4 is ubiquitinylated by RAD23 and its degradation negatively regulates repair (Lommel et al, 2002). The 19S regulatory complex of the proteasome has also been reported to affect NER, independent of RAD23, of proteolysis, and of binding to the 20S component (Gillette et al, 2001), indicating that this complex may have unexpected roles in addition to regulating proteolysis.…”

“…Further, upstream regulatory components that bind to the basic proteasome structure have evolved that modulate activity. Certain of these regulatory components, once considered integral proteasomal structures, have recently been suggested to have additional independent functions (Gillette et al, 2001). Modulation of proteasome activity has been shown to affect cellular processes as diverse as transcriptional activation (Ejkova and Tansey, 2002;Kang et al, 2002;Ottosen et al, 2002), cell cycle progression (Yamaguchi and Dutta, 2000), cell survival (Delic et al, 1998;, DNA repair and chromosome stability (Arnold and Grune, 2002), receptor-mediated responses to external ligands (Strous and van Kerkhof, 2002), and antigen presentation through the MHC class I-mediated pathway (Rock et al, 2002).…”