THE 5'-UNTRANSLATED REGION OF GLUT1 GLUCOSE-TRANSPORTER MESSENGER-RNACAUSES DIFFERENTIAL REGULATION OF THE TRANSLATIONAL RATE IN PLANT ANDANIMAL SYSTEMS

The blood-brain barrier GLUT1 glucose transporter is under post-transc riptional regulation, and the 5'-untranslated region (5'-UTR) of the G LUT1 mRNA increases its translational rate in mammalian cells. To obta in more insight into the mechanism of translational control of GLUT1, the present investigation studied the translational efficiency of capp ed full length synthetic human (h) and rabbit (rab) GLUT1 mRNA and bot h 5'- and 3'-UTR deleted hGLUT1 mRNAs in both mammalian and plant cell free translation systems. Translation efficiency of both h-and rabGLU T1 mRNA was increased 3- to 6-fold in rabbit retyculocyte lysate (RRL) compared with wheat germ extract (WGE). Confirming previous observati ons, deletion of 5'- and 5'/-3'-UTR markedly reduced the translation e fficiency of the h-GLUT1 transcript in RRL. On the contrary, these del etions markedly increased the translation of GLUT1 in WGE. The present data provide additional evidence suggesting that the 5'-UTR of the GL UT1 mRNA contains cis-acting elements involved in the translational ac tivation of the GLUT1 gene in mammalian cells and that factors involve d in this cis/trans-acting interaction are either absent or down-regul ated in plant systems. (C) 1997 Elsevier Science Inc.