Delayed accumulation of the yeast G₁ cyclins Cln1 and Cln2 and the F‐box protein Grr1 in response to glucose

Abstract

The ability to integrate nutrient availability into cell cycle regulation is critical for the viability of organisms. The Saccharomyces cerevisiae ubiquitin ligase SCF(Grr1) regulates the stability of several proteins that participate in cell division or nutrient sensing. Two of its targets, the cyclins Cln1 and Cln2, accumulate in the presence of glucose. When glucose is added to cells growing asynchronously, we show that the accumulation of the cyclins is a very slow response. We report that the F-box protein Grr1 also accumulates at higher levels in the presence of glucose, and that the response to glucose follows a delayed pattern strikingly similar to that described for Cln1 and Cln2. A model for the regulation of F-box proteins predicts that substrate accumulation could stabilize Grr1. While we found that Grr1 is more stable in cells growing with glucose, we show that the delayed responses to glucose occur independently: Grr1 accumulates in the absence of the cyclins, and vice versa. Thus, our results indicate that this model might not apply to the cyclins and Grr1. Glucose is known to strengthen the interaction of Grr1 with Skp1 in the SCF complex. We hypothesize that glucose could promote the accumulation of Grr1 and its assembly into a SCF complex as a feedback regulation that helps compensate for higher cyclins levels.

Activation of the S-Phase Checkpoint Inhibits Degradation of the F-Box Protein Dia2

“…4B). Rather, the skp1-11 and cdc53-1 mutants appeared to increase the turnover rate of Dia2, as has been observed for the Grr1 and Met30 F-box proteins (12,24,29,38). Similar results were observed for the skp1-12 temperature-sensitive strain (data not shown).…”

“…Additionally, other F-box proteins are stabilized in SCF pathway mutants; however, this is not the case for Dia2 (13,47). Rather, Dia2 is even less stable in skp1-11 and cdc53-1 mutants, consistent with the observation that other F-box proteins are destabilized when core SCF components are defective (12,24,29,38). Some F-box proteins are targets of other ubiquitin ligases, such as the APC/C.…”

“…For example, some F-box proteins have been shown to be targeted for ubiquitin-mediated destruction via an autoubiquitination mechanism (13,47). Conversely, loss of SCF components appears to negatively affect the stability of some F-box proteins (12,24,29,38). Alternatively, F-box proteins may be targeted for destruction by non-SCF ubiquitin ligases.…”

The replication stress response and the ubiquitin system: a new link in maintaining genomic integrity

“…In vitro , many F-box proteins can serve as substrates in autoubiquitination reactions [24], but the extent to which this process occurs in vivo is unclear. By contrast, a few F-box proteins are destabilized when SCF components are impaired [25-28]. Moreover, some F-box proteins are targeted for degradation by SCF-independent pathways.…”

Regulation of the conserved 3′‐5′ exoribonuclease EXOSC10/Rrp6 during cell division, development and cancer

“…Ubiquitination requires so‐called E3 ligases (writers), ubiquitin‐binding effectors (readers), and deubiquitylases (erasers) that work together to establish the protein concentration, conformation and localization needed for robust cell growth and development (Oh, Akopian & Rape, 2018). Rrp6 physically interacts with binds ubiquitin ligase 2 (Bul2), a subunit of the reverses spt phenotype 5 (Rsp5) E3‐ubiquitin ligase important for growth during stress (Kaida, Toh‐e & Kikuchi, 2003; Frattini et al ., 2017), the ubiquitin‐activating enzyme (E1) Uba1, the ubiquitin conjugating enzyme (E2) Ubc1, which is associated with the APC/C (Girard, Tenthorey & Morgan, 2015; Gonzales‐Zubiate et al ., 2017) and Grr1, a glucose‐responsive subunit of the Skp1‐Cullin‐F‐box protein (SCF) ubiquitin‐ligase complex (Fey & Lanker, 2007; Gonzales‐Zubiate et al ., 2017).…”