Redox-sensitive E2 Rad6 controls cellular response to oxidative stress via K63-linked ubiquitination of ribosomes

The ubiquitin conjugase Rad6 mediates ribosome pausing during oxidative stress

“…In addition, the effect of Rad6 on peroxide-induced translational repression was reproducible in the S288C background (Figure S3B-C). These findings are also in agreement with previous data showing higher puromycin incorporation in rad6 cells in the presence of peroxide compared to WT cells (Simoes et al, 2022). Overall, our results show that Rad6 is necessary for the oxidative stress-induced translational repression.…”

“…UBE2A was also shown to modulate neuronal function in flies by interacting with the E3 ubiquitin ligase Parkin and thereby inducing mitophagy (Haddad et al, 2013). We previously showed that Rad6 carrying the corresponding disease mutations in its human homolog leads to dysregulated K63 ubiquitination response during oxidative stress in yeast (Simoes et al, 2022), further supporting the idea that the role of Rad6 in cellular homeostasis is conserved across species. Our studies in yeast, therefore, reveal crucial insights into the cellular response to UBE2A deficiency and could be important for delineating the disease mechanisms.…”

“…Despite impaired eIF2 phosphorylation, Gcn4 is still constitutively translated (Figure 6) in rad6 cells (Gcdphenotype) even in the absence of oxidative stress, which is potentially indicative of an initiation defect (Hinnebusch, 2005). An initiation defect would also be consistent with the slower growth of rad6 cells (Simoes et al, 2022) and overall lower translation rate in the absence of peroxide (Figures 4B-C and S3). One possibility for the Gcdphenotype could be that the lack of Rad6 affects the expression of "Gcd" genes and decreases their availability, resulting in uORF bypassing and increased translation of GCN4.…”

“…We named this pathway redox control of translation by ubiquitin (RTU) (Dougherty et al, 2020). A key regulator of the RTU is the E2 ubiquitin conjugase Rad6 that rapidly modifies ribosomal proteins with K63-linked polyubiquitin chains in response to H 2 O 2 (Back et al, 2019; Silva et al, 2015; Simoes et al, 2022; Zhou et al, 2020). Ubiquitinated ribosomes arrest at the pre-translocation stage of translation elongation (Zhou et al, 2020) and are proposed to participate in the shutdown of protein production during stress (Back et al, 2019; Zhou et al, 2020).…”

“…Ubiquitinated ribosomes arrest at the pre-translocation stage of translation elongation (Zhou et al, 2020) and are proposed to participate in the shutdown of protein production during stress (Back et al, 2019; Zhou et al, 2020). Furthermore, we recently showed that deletion of RAD6 prevents K63-linked ubiquitination of ribosomes and leads to continued protein production under oxidative stress and dysregulated levels of antioxidant proteins (Simoes et al, 2022). Rad6 is a multifunctional and highly conserved protein, in which mutations to its human homolog UBE2A are associated with the X-linked intellectual disability type Nascimento (Bruinsma et al, 2016; Nascimento et al, 2006).…”