Sequence diversity in the 5' untranslated region of rabbit muscle phosphofructokinase mRNA

DNA sequences of two full-length rabbit muscle phosphofructokinase (RMPFK) cDNAs (A and B) show identical coding sequence but heterogeneous 5' untranslated regions. cDNA-A is formed by removal of a 1.7 kb upstream intron while cDNA-B retains the 3' region of this intron. A 2.8 kb upstream sequence of RMPFK gene contains several features characteristic of housekeeping genes: high GC content (67%) at its 5' end, with 50 CpG sites; five Sp1 sites; and no functional TATA box. Comparison of the 5' sequences of the two RMPFK cDNAs and three human muscle PFK cDNAs (Nakajima, H., et al., (1990) Biochem. Biophys. Res. Com. 166, 637) suggests that a single splicing event occurs involving different splicing donor sites but the same splicing acceptor site, resulting in diversity in the upstream sequence. These observations suggest that transcription of muscle PFK gene may start at multiple sites, another feature of housekeeping genes.