Myosin heavy-chain mRNA is present in both myofibrillar and subsarcolemmal regions of muscle fibres.
Hybridization in situ with riboprobes to the myosin heavy-chain slow isoform showed that, in the rat soleus muscle, the myosin heavy-chain mRNA was distributed throughout the myofibres. There was greater density of autoradiographic grains in the subsarcolemmal regions of the fibres, but there was also a considerable number of grains in the core myofibrillar region of the fibres. Microdensitometry showed that the grain density in the myofibrillar region was approximately half that in the subsarcolemmal rim; this would correspond to some 70% of the mRNA being present in the myofibrillar region. The results are consistent with the hypothesis that myosin is synthesized on polyribosomes present in the intermyofibrillar cytoplasm.
Division of Biochemical Sciences, Rowett Research Institute, Aberdeen, Scotland, U.K.
J
J
Hesketh
G
G
Campbell
N
N
Loveridge
D000818:Animals; D001345:Autoradiography; D008297:Male; D009210:Myofibrils / Q000737:chemistry*; D009218:Myosins / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D012508:Sarcolemma / Q000737:chemistry*
D012333:RNA, Messenger; D009218:Myosins