Multiple mRNAs for 3-hydroxy-3-methylglutaryl coenzyme A reductase determined by multiple transcription initiation sites and intron splicing sites in the 5'-untranslated region.

The current studies show that mRNAs with 16 different 5'-untranslated regions (varying in length from 68 to 670 nucleotides) are produced from the 3-hydroxy-3-methylglutaryl coenzyme A reductase gene in hamster UT-1 cells. This complex pattern of mRNAs results from a combination of multiple transcription initiation sites and multiple 5' splice donor sites for the intron in the 5'-untranslated region of the gene. Analysis of the multiple mRNAs was made possible by a modification of the S1 nuclease technique in which we used a series of progressively truncated uniformly labeled, single-stranded [32P]DNA probes in addition to the usual end-labeled 32P-probes. All of the reductase mRNAs are diminished when UT-1 cells are incubated with sterols, indicating that all of them are subject to coordinate control.