Calf Crystallin Synthesis in Frog Cells: The Translation of Lens-Cell 14S RNA in Oocytes

Abstract

14S RNA isolated from calf-lens polyribosomes was injected into oocytes of the frog Xenopus laevis. Oocytes injected with 14S RNA and buffer contained a protein resembling the A2 chain of calf alpha-crystallin; oocytes injected with buffer alone contained no crystallin-like material. alphaA2 crystallin polypeptides were identified by various criteria: urea-gel electrophoresis under acidic and basic conditions, gel electrophoresis in sodium dodecyl sulfate, N-terminal analysis, and paper chromatography of methionine-containing tryptic peptides. It is concluded that when it is injected into a living frog oocyte, the 14S RNA from lens tissue is reasonably stable and has the properties of an alphaA2 crystallin messenger. The messenger requires no lens cell-specific components for translation within the oocyte, and the translational machinery of the frog cell will accept messenger RNA from a totally different cell type from another species. The A2 chains of alpha-crystallin extracted from lens tissue possess an acetylated N-terminal methionine residue; the N-terminal methionine of alphaA2 chains derived from frog oocytes injected with 14S RNA was also acetylated.