Analysis of the spontaneous mutator phenotype associated with 20S proteasome deficiency in S. cerevisiae

Distinct consequences of posttranslational modification by linear versus K63-linked polyubiquitin chains

“…Genetic data linking DNA damage bypass to proteasome activity have been indirect and ambiguous. While Hofmann and Pickart (15) used a lack of synergism between pre1-1 pre2-2 and rev3 mutants with respect to UV sensitivity as an argument against proteolytic function in error-free damage tolerance, others postulated a role of the proteasome in limiting the mutagenic activity of TLS, based on epistasis and mutation rate analysis (24,28). We have finally directly assessed the response of polyubiquitylated PCNA to variations in proteasome activity and find no evidence for a degradation of the modified clamp.…”

The Ubiquitin-Proteasome System and DNA Repair

“…This spontaneous mutator phenotype has been verified to be primarily PRR-based and unrelated to the HR and NER pathways (McIntyre et al, 2006). Knock-out of Rev3, which encodes the catalytic subunit of Pol , in an Ump1-deficient yeast strain correlates with a dramatic decrease in the frequency of UV-induced and spontaneous mutations, thereby suggesting that Ump1 may serve as a negative regulator of Rev3 (Podlaska et al, 2003;McIntyre et al, 2006;Wiltrout & Walker, 2011). In contrast, the presence of Rad30, which encodes Pol , in an Ump1-deficient background is associated with increased UV-sensitivity but a decrease in the frequency of spontaneous mutations (Podlaska et al, 2003;McIntyre et al, 2006).…”

“…Importantly, this phenotype is characteristic of yeast strains with defects in PRR, and Podlaska and colleagues have determined that these genes are members of the Rad6/Rad18 epistasis group (Podlaska et al, 2003). This spontaneous mutator phenotype has been verified to be primarily PRR-based and unrelated to the HR and NER pathways (McIntyre et al, 2006). Knock-out of Rev3, which encodes the catalytic subunit of Pol , in an Ump1-deficient yeast strain correlates with a dramatic decrease in the frequency of UV-induced and spontaneous mutations, thereby suggesting that Ump1 may serve as a negative regulator of Rev3 (Podlaska et al, 2003;McIntyre et al, 2006;Wiltrout & Walker, 2011).…”

“…The error-prone method, referred to as DNA translesion synthesis (TLS), is carried out by a TLS polymerase such as Pol , Pol , Pol , Pol , or Rev1 (Prakash et al, 2005). Rad6, an E2 enzyme, and Rad18, a DNA-binding protein, form a complex that governs PRR and is responsible for PCNA modification, a crucial event in this DNA repair pathway (Hoege et al, 2002;McIntyre et al, 2006).…”

“…Knock-out of Rev3, which encodes the catalytic subunit of Pol , in an Ump1-deficient yeast strain correlates with a dramatic decrease in the frequency of UV-induced and spontaneous mutations, thereby suggesting that Ump1 may serve as a negative regulator of Rev3 (Podlaska et al, 2003;McIntyre et al, 2006;Wiltrout & Walker, 2011). In contrast, the presence of Rad30, which encodes Pol , in an Ump1-deficient background is associated with increased UV-sensitivity but a decrease in the frequency of spontaneous mutations (Podlaska et al, 2003;McIntyre et al, 2006). Taken together, these results suggest that Rev3 and Rad30 are epistatic to Ump1 and that mutations caused by proteasomal defects depend upon both Pol and Pol (Podlaska et al, 2003;McIntyre et al, 2006).…”