UNCOORDINATED INHIBITION OF GENE-EXPRESSION FOR MUSCLE PROTEINS BY A TROPONIN-T ANTISENSE OLIGODEOXYNUCLEOTIDE

The effect of antisense oligodeoxynucleotide to rat troponin T (TnT) m RNA on its expression in differentiated rat L6 myotubes in culture was examined. The target sequence following the initiation codon was betw een nucleotides 83 and 97 and is found in all mRNAs produced from the f-TNT gene. Our studies showed that chimeric oligomer with one phospho rothioate linkage at the 3'-end was considerably more resistant to nuc leases than was a phosphodiester oligomer, The chimeric oligomer produ ced >50% inhibition of TnT polypeptide synthesis. Synthesis of myosin heavy chain (MHC), troponin I (TnI), and alpha and beta tropomyosins ( Tm) was not inhibited by the anti-TnT oligomer, However, synthesis of alpha-actin and troponin C (TnC) was somewhat affected by this treatme nt. Furthermore, compared with the untreated control myotubes, the ste ady-state level of TnT mRNA was reduced by approximately 40%-50% in an ti-TnT oligomer-treated myotubes. Cellular levels of three other muscl e mRNAs, alpha-Tm, s-TnI, and alpha-actin were also reduced by approxi mately 30%-40%. In contrast, fast TnI, beta-Tm, and TnC mRNA levels we re not significantly affected by this treatment, Therefore, inhibition of TnT synthesis in differentiated myotubes uncoupled the coordinated expression of muscle proteins.