E2 ubiquitin-conjugating enzyme Ubc11 regulates Rst2 protein stability in the fission yeast Schizosaccharomyces pombe

In Schizosaccharomyces pombe, many transcription factors, including Rst2, remain poorly understood. Rst2 functions downstream of the cAMP-PKA pathway, but its protein stability and potential degradation via the ubiquitin-proteasome system, are not well characterized. This study investigates the -regulation of Rst2 in S. pombe, focusing on expression and degradation via the ubiquitin-proteasome system and E2 enzymes. Protein expression and stability were analyzed by western blotting to assess the impact of E2 mutations on Rst2 regulation. Rst2 transcription remained low at early time points but increased over fourfold by 24 h, remaining elevated through 48 h. Protein stability assays showed rapid Rst2 degradation under cycloheximide (CHX) treatment, while CHX and bortezomib (BZ) treatment preserved Rst2 protein levels, indicating the proteasome-dependent degradation of Rst2. To determine which E2 enzyme(s) are invovled in Rst2 degradation, we individually deleted all non-essential E2 genes and generated two point mutants ubc4-P61S and ubc11-P93L mutant and found that Rst2 is stabilized only in ubc11-P93L. This study shows the role of the ubiquitin-proteasome system and E2 enzyme Ubc11 in regulating Rst2 in S. pombe.