Coregulation of Alternative Transcripts of the STA2 Gene in the Yeast Saccharomyces cerevisiae

It is known that upon STA2 gene expression in Saccharomyces cerevisiae cells, two transcripts of different lengths are formed. These fragments contain different start codons of translation (AUG1 and AUG2) located in the same reading frame. The ratio between expression levels of proteins translated from AUG1 and AUG2 was invariably about 2 : 7 and did not depend on the choice of the reporter product (secreted glucoamylase (GA) or β-galactosidase accumulated in cells). Neither this ratio depended on glucose repression/derepression. Based on the assumed proportional relationship between levels of transcription and translation of the STA2 gene in yeast cells, all these results cumulatively indicate that the two STA2 transcripts are coregulated. The production of secreted GA was also shown to be markedly stimulated at the posttranscriptional level under conditions of glucose repression.