Academic Press Inc Elsevier Science Acta Medica Okayama 0006-291X 411 3 2011 Ubiquitin chains in the Dsk2 UBL domain mediate Dsk2 stability and protein degradation in yeast 555 561 EN Takeshi Sekiguchi Toru Sasaki Minoru Funakoshi Takashi Ishii Yoh-hei Saitoh Shu-ichi Kaneko Hideki Kobayashi Ubiquitin-like (UBL)-ubiquitin-associated (UBA) proteins, including Dsk2 and Rad23, act as delivery factors that target polyubiquitinated substrates to the proteasome. We report here that the Dsk2 UBL domain is ubiquitinated in yeast cells and that Dsk2 ubiquitination of the UBL domain is involved in Dsk2 stability, depending on the Dsk2 UBA domain. Also, Dsk2 lacking ubiquitin chains impaired ubiquitin-dependent protein degradation and decreased the interaction of Dsk2 with polyubiquitinated proteins in cells. Moreover, Dsk2 ubiquitination affected ability to restore the temperature-sensitive growth defect of dsk2 Delta. These results indicate that ubiquitination in the UBL domain of Dsk2 has in vivo functions in the ubiquitin-proteasome pathway in yeast. No potential conflict of interest relevant to this article was reported.