Two types of mRNA encoding myosin regulatory light chain in carp fast skeletal muscle differ in their 3' non-coding regions and expression patterns following temperature acclimation.

cDNA clones encoding the myosin regulatory light chain (RLC) were isolated from a cDNA library prepared from fast skeletal muscle of the carp Cyprinus carpio L. Two types of cDNA clone encoding carp RLC were found with identical deduced amino acid sequences. The two mRNAs differed in the number of polyadenylation signals prior to the poly(A) tail in the 3' non-coding region. The two mRNA species, with approximate sizes of 1.4 and 0.8 kilobases, were also observed in northern blot analysis. Carp were acclimated for a minimum of 5 weeks to either 10 degrees C or 30 degrees C (14h:10h light:dark photoperiod). The total levels of mRNA transcripts coding for the RLC and myosin heavy chain were, respectively, 3.3 and 3.9 times higher in cold-than in warm-acclimated fish. Differences in the levels of RLC in mRNA transcripts were largely due to the concentration of the 1.4 kilobase mRNA species.