Stress resistance in Saccharomyces cerevisiae is strongly correlated with assembly of a novel type of multiubiquitin chain.

Abstract

The covalent attachment of ubiquitin (Ub) to short-lived or damaged proteins is believed to be the signal that initiates their selective degradation. In several cases, it has been shown that the proteolytic signal takes the form of a multi-Ub chain in which successive Ub molecules are linked tandemly at lysine 48 (K-48). Here we show that Ub molecules can be linked together in vivo at two other lysine positions, lysine 29 (K-29) and lysine 63 (K-63). The formation of these alternative linkages is strongly dependent on the presence of the stress-related Ub conjugating enzymes UBC4 and UBC5. Furthermore, expression of Ub carrying a K-63 to arginine 63 substitution in a strain of Saccharomyces cerevisiae that is missing the poly-Ub gene, UBI4, fails to compensate for the stress defects associated with these cells. Taken together, these results suggest that the formation of multi-Ub chains involving K-63 linkages plays an important role in the yeast stress response. In broader terms, these results also suggest that Ub is a versatile signal in which different Ub chain configurations are used for different functions.

U Box Proteins as a New Family of Ubiquitin-Protein Ligases

“…A short lysine 29-linked chain might thus constitute a signal to recruit E4 before proteasomal proteolysis (35). Polyubiquitination through lysine 63 of ubiquitin appears to mark proteins that contribute to DNA repair (41), to the cellular response to stress (42), to inheritance of mitochondrial DNA (43), to endocytosis of certain plasma membrane proteins (44), or to ribosomal function (45). In addition, TRAF6, a RING finger-type E3, in conjunction with the E2 Ubc13 and and the Ubc-like protein Uev1A, targets lysine 63 of ubiquitin and plays an important role in IB phosphorylation in the NF-B signaling pathway (46).…”

Budding yeast Dsk2p is a polyubiquitin-binding protein that can interact with the proteasome

“…Polyubiquitin chains can be formed in vivo by at least three different linkages of lysine residues in the Ub molecule, K29, K48, and K63 (30)(31)(32)(33). Next, a series of Ub lysine mutants, K29R, K48R, K63R, or the triple substitution mutant, were made, and the effects of Ub lysine mutants on polyubiquitin-Dsk2p binding were examined (Fig.…”

Sequence and Transcriptional Analysis of the Ubiquitin Gene Cluster in the Genome of Spodoptera exigua Nucleopolyhedrovirus

“…In this pathway ubiquitin monomers are covalently linked by their C-terminal Gly-76 to lysine residues of target proteins and to internal lysines of other ubiquitin molecules or to form multi-ubiquitin chains. Recently, it has been shown that Lys-63 and Lys-29 of ubiquitin can also be used as acceptors for ubiquitination (Arnason & Ellison, 1994, Johnson et al, 1995. Ubiquitination has been implicated strongly in protein degradation (Doherty & Mayer, 1992).…”