Abstract
The yeast ubiquitin-like and ubiquitin-associated protein Dsk2 is one of the ubiquitin receptors that function in the ubiquitin-proteasome pathway. We screened the Dsk2-interacting proteins in Saccharomyces cerevisiae by a two-hybrid assay and identified a novel Dsk2-interacting protein, Irc22, the gene locus of which has previously been described as YEL001C, but the function of which is unknown. IRC22/YEL001C encodes 225 amino acid residues with a calculated molecular weight of 25 kDa. The Irc22 protein was detected in yeast cells. IRC22 was a nonessential gene for yeast growth, and its homologs were found among ascomycetous yeasts. Irc22 interacted with Dsk2 in yeast cells, but not with Rad23 and Ddi1. Ubiquitin-dependent degradation was impaired mildly by over-expression or disruption of IRC22. Compared with the wild-type strain, dsk2Δ exhibited salt sensitivity while irc22Δ exhibited salt tolerance at high temperatures. The salt-tolerant phenotype that was observed in irc22Δ disappeared in the dsk2Δirc22Δ double disruptant, indicating that DSK2 is positively and IRC22 is negatively involved in salt stress tolerance. IRC22 disruption did not affect any responses to DNA damage and oxidative stress when comparing the irc22Δ and wild-type strains. Collectively, these results suggest that Dsk2 and Irc22 are involved in salt stress tolerance in yeast.
Highlights
The ubiquitin-proteasome pathway plays a crucial role in the control of various cellular processes by mediating the degradation of many short-lived proteins
Irc22 interacts with Dsk2 but not with Rad23 and Ddi1
We screened for proteins that interacted with Dsk2 in a two-hybrid system
Summary
The ubiquitin-proteasome pathway plays a crucial role in the control of various cellular processes by mediating the degradation of many short-lived proteins. Rpn13 [10,11,12,13,14,15], E1/E2/E3 enzymes [16,17,18], and several accessory proteins [19,20,21,22] Those interactions are positively and negatively involved in the recognition and regulation of the ubiquitin-proteasome pathway: Via their UBL domains, Rad and Dsk interact with the ubiquitin ligase E4 (Ufd2) that is defined as a ubiquitin chain-extending activity, and the Rad23-Ufd interaction helps to recognize ubiquitinated substrates [19,22]. A link between ubiquitin-dependent degradation and salt stress responses has been recently reported in plants: the proteasomal receptor Rpn10 [41], ubiquitin-conjugating enzyme E2 [42], ubiquitin ligase E3 [43], and ERAD components [42,44]. Possible roles of Dsk and Irc in salt stress in yeast are discussed
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