Expression of mouse phosphofructokinase-M gene alternative transcripts: evidence for the conserved two-promoter system.

Molecular cloning of the 5' part of mouse phosphofructokinase-M cDNA was performed. In the 46 cDNA clones isolated, there were two classes of 5' untranslated sequences. One had an EcoRI site within its 5' untranslated sequence. This showed 83.0% similarity with human type B mRNA for phosphofructokinase-M. The other lacked an EcoRI site, showing 92.9% similarity with human type C mRNA. Using the reverse-transcription PCR technique, we found that the transcript with an EcoRI site was exclusively expressed in cardiac and skeletal muscles, while that without an EcoRI site was expressed in all the mouse tissues examined. The results suggested that the mouse phosphofructokinase-M gene was transcribed through alternative splicing by the multiple promoters. This transcription mechanism was considered to be evolutionarily conserved. The level of phosphofructokinase-M gene expression in mouse cardiac and skeletal muscles decreased in the ketotic diabetic state. Although the regulatory mechanism and the physiological significance are not fully known, this would indicate that phosphofructokinase-M gene transcripts are affected during the diabetic state.