Yeast Elc1 plays an important role in global genomic repair but not in transcription coupled repair

Transcription coupled repair (TCR) is a nucleotide excision repair (NER) pathway that is dedicated to repair in the transcribed strand of an active gene. The genome overall NER is called global genomic repair (GGR). Elc1, the yeast homolog of the mammalian elongation factor elongin C, has been shown to be a component of a ubiquitin ligase complex that contains Rad7 and Rad16, two factors that are specifically required for GGR. Elc1 has also been suggested to be present in another ubiquitin ligase complex that lacks Rad7 and Rad16 and is involved in UV-induced ubiquitylation and subsequent degradation of RNA polymerase II. Here we show that elc1 deletion increases UV sensitivity of TCR-deficient cells but does not affect the UV sensitivity of otherwise wild type and GGR-deficient cells. Cells deleted for elc1 show normal NER in the transcribed strand of an active gene but have no detectable NER in the non-transcribed strand. Elc1 does not affect UV-induced mutagenesis when TCR is operative, but plays an important role in preventing the mutagenesis if TCR is defective. Furthermore, the levels of Rad7 and Rad16 proteins are not significantly decreased in elc1 cells, and overexpression of Rad7 and Rad16 individually or simultaneously in elc1 cells does not restore repair in the non-transcribed strand of an active gene. Our results suggest that Elc1 has no function in TCR but plays an important role in GGR. Furthermore, the role of Elc1 in GGR may not be subsidiary to that of Rad7 and Rad16. (C) 2008 Elsevier B.V. All rights reserved.