TERMINAL DIFFERENTIATION-DEPENDENT ALTERATION IN THE EXPRESSION OF TRANSLATION ELONGATION FACTOR-1-ALPHA AND ITS SISTER GENE, S1, IN NEURONS

Elongation factor-1 alpha (EF-1 alpha) is a highly conserved, abundant ly expressed protein that functions in peptide elongation during mRNA translation. Mammalian species contain a second EF-1 alpha gene, S1, w hose expression is limited to brain, heart, and skeletal muscle. Such tissue specificity in S1 gene expression led us to hypothesize that th is specialized member of the EF-1 alpha family is possibly essential t o terminally differentiated, long-lived cells such as neurons, cardiom yocytes, and myocytes. We report here that during development, EF-1 al pha mRNA levels remain unchanged in S1-negative tissues, but sharply d ecrease in S1-positive tissues. RNase protection as well as tissue dis tribution analyses of the S1 message suggest that down-regulation of E F-1 alpha expression coincides well with that of S1 up-regulation duri ng postnatal development. Analysis of primary cultures of the rat neon atal cerebral cortex cells has shown that S1 gene expression is indeed restricted to neurons only, whereas nonneuronal cell types such as as trocytes and microglia are S1-negative. EF-1 alpha mRNA on the other h and was detected in all three cell types, namely, neurons, astrocytes, and microglia. This report confirms the terminal differentiation-depe ndent expression of the S1 gene in neurons of the cerebral cortex. (C) 1995 Academic Press, Inc.