Transcriptional regulation of two genes specifically induced by glucose starvation in a hamster mutant fibroblast cell line.

This report concerns the characterization of the RNA transcripts encoded by two cDNA sequences p4A3 and p3C5, derived from a hamster temperature-sensitive mutant cell line K12. Using the two cDNA sequences as hybridization probes, we show that they occur as single copy genes in the hamster genome and encode for RNA transcripts which are highly inducible in K12 cells at 40.5 degrees C. After incubation at 40.5 degrees C for 16 h, there is a 10-fold increase in the p4A3 and p3C5 mRNA levels, reaching a final concentration of about 1% of the cytoplasmic polyadenylated RNA. We demonstrate that the kinetics of transcription of p4A3 and p3C5 directly parallel the accumulation of the mRNA levels at 40.5 degrees C. Thus, our data indicate that the expression of these two genes are primarily regulated at the transcriptional level. In addition, there is a 3- to 4-fold increase in the p4A3 and p3C5 mRNA levels when the cells are specifically starved of glucose. This implies that the expression of these two genes are stringently regulated by the availability of glucose in the culture medium. The relationship between the cDNA clones and two glucose-regulated proteins which are overproduced in K12 cells at 40.5 degrees C is discussed.