3 GENES UNDER DIFFERENT DEVELOPMENTAL CONTROL ENCODE ELONGATION FACTOR-1-ALPHA IN XENOPUS-LAEVIS

We have cloned cDNAs encoding two variants of the elongation factor for protein synthesis in Xenopus laevis, called EF-1α. One of these (42Sp50) is expressed exclusively in immature oocytes. It is one of two protein components of a 42S RNP particle that is very abundant in previtellogenic oocytes. The 42S RNP particle consists of various tRNAs, 5S RNA, 42Sp50 and a 5S RNA binding protein (42Sp43). A major function served by 42Sp50 appears to be the storage of tRNAs for later use in oogenesis and early embryogenesis. The second EF-1α variant (EF-1α) is expressed mainly in oocytes but transiently in early embryogenesis as well. Its mRNA cannot be detected after neurulation in somatic cells. EF-1αO is closely related to a third EF-1α (EF-1αS), discovered originally by Krieg et al. (1). EF-1αS is expressed at low levels in oocytes but actively in somatic cells. The latter two proteins are very similar to known eukaryotic EF-1α from other organisms and presumably function in their respective cell types to support protein synthesis. © 1990 Oxford University Press.