DIFFERENTIAL EXPRESSION OF S1 AND ELONGATION FACTOR-1-ALPHA DURING RAT DEVELOPMENT

Elongation factor-1alpha (EF-1alpha) is a highly conserved protein fun ctioning in peptide elongation during translation. A cDNA, S1, was iso lated; its deduced amino acid sequence shares high similarity with mam malian EF-1alphas (92%). While EF-1alpha is present in all tissues, S1 mRNA can only be detected in brain, heart, and muscle. We report here that the retropseudogene phenomenon is attributable to EF-1alpha and not S1, the latter being represented by a single copy in the rat genom e. The S1 steady-state mRNA levels are consistently higher than EF-1al pha in S1-positive tissues. S1 mRNA can only be detected late during b rain, heart, and muscle development in vivo and increases to a plateau in early postnatal life. In a cultured muscle system, S1 expression i s dependent upon the formation of myotubes, although the accumulation of S1 mRNA is significantly lower than that observed in adult skeletal muscle. EF-1alpha mRNA levels are down-regulated during brain, heart, and muscle development, but stay relatively steady in liver. We show here that EF-1alpha and S1 are differentially expressed during rat dev elopment and that the activation of S1 gene expression is subsequent t o the terminal differentiation process in brain, heart, and muscle.