Glucose-inducible expression of rrg1⁺ in Schizosaccharomyces pombe: Post-transcriptional regulation of mRNA stability mediated by the downstream region of the poly(A) site

rrg1⁺ (rapid response to glucose) has been isolated previously as a UV-inducible gene in Schizosaccharomyces pombe, designated as uvi22⁺. However, it was revealed that the transcript level of this gene was regulated by glucose, not by DNA-damaging agents. Glucose depletion led to a rapid decrease in the level of rrg1⁺ mRNA, by ∼50% within 30 min. This effect was readily reversed upon re-introduction of glucose within 1 h. High concentrations (4 and 8%) of glucose showed similar effects on increasing the rrg1⁺ mRNA level compared with 2% glucose, while a low concentration (0.1%) was not effective in raising the rrg1⁺ mRNA level. In addition, sucrose and fructose could increase rrg1⁺ mRNA level. Interestingly, the rapid decline in mRNA level seen upon glucose deprivation resulted from precipitous reduction of mRNA half-life. Serial and internal deletions within the 3′-flanking region of rrg1⁺ revealed that a 210-nt region downstream of the distal poly(A) site was critical for glucose-regulated expression. Moreover, this downstream region participated in 3′-end formation of mRNA. Taken together, this is the first report on glucose-inducible expression regulated posttranscriptionally by control of mRNA stability in S.pombe.