Effects of Insulin on Gene Transcription

for these changes in mRNA concentration. The steady-state concentration of a messenger RNA is determined by a sequence of events that includes initiation of transcription by RNA polymerase II, elongation of the trans cr ipt , termina­ tion of transcription, mRNA capping, polyadenylation, splicing, transport to the cytoplasm, and eventual degradation. Recent progress in the study of eukaryotic gene expression demonstrates that the first step in this process, initiation of transcription, can be regulated by the binding of nuclear proteins to cis-actin g DNA sequences (26). For example, DNA-binding proteins are known to mediate transcription al effects of steroid hormones, cAMP, and various low-molecu lar-weight effectors. This is not a well established mech­ anism of action for peptide hormones. Whether the effects of insulin on enzyme concentration result from this type of transcriptional regulation is the