CONTROL OF THE MURINE PHOSPHOFRUCTOKINASE-A GENE DURING MUSCLE DIFFERENTIATION

The muscle-specific isoform of phosphofructokinase (PFK-A) is induced during muscle development. To understand expression of PFK at the mole cular level, transcription of the mouse PFK-A gene was examined during C2 myoblast differentiation to myotubes. PFK-A gene transcription inc reased 5-7-fold during differentiation in vitro. To identify cis-actin g elements which direct muscle-specific transcription of the PFK-A gen e, its 5'-flanking region and first exon were cloned and characterized . S1 nuclease protection and primer extension assays showed four sites of transcription initiation at 106, 105, 88, and 87 bp upstream of th e translation initiation codon. Stable transfect ion of fusion genes l inking-1900 to +99 of PFK-A 5'-flanking Sequence to chloramphenicol ac etyltransferase coding sequences into myogenic C2 cell did not confer muscle-specific expression. However larger fragments of PFK-A 5'-flank ing region (-5800 to +99) showed muscle-specific expression by transie nt transfection assay. The sequences directing muscle-specific transcr iption were further defined by linking various PFK-A upstream fragment s to the luciferase gene under the control of the PFK-A proximal promo ter, -335 to +99 bp. We found DNA sequence responsible for muscle-spec ific expression of the PFK-A gene between -4800 and -3900 bp.