The effect of reticulocyte ribosome “factors” on the translation of haemoglobin messenger RNA in living frog oocytes

Abstract

1. The effect of ribosome “factors” (materials released from polysomes by 0.5 or 1.0 M KCl) on the translation of messenger RNA has been tested by injecting factors and mRNA into living frog oocytes. Factors were prepared from mammalian reticulocytes as well as from frog oocytes and were tested with Hb mRNA from mammalian reticulocytes. Injected oocytes were labelled with amino acids during incubation, and the effect of factors was judged from the ratio of labelled haemoglobin to labelled oocyte proteins synthesised by injected oocytes. 2. The factors released from reticulocyte ribosomes by KCl may contain up to 30 % of the total haemoglobin message activity of reticulocyte polysomes. When Hb mRNA was supplied at a low concentration so that its supply limited the rate of haemoglobin synthesis, reticulocyte factors had no effect on its translation. When Hb mRNA was supplied at a high enough concentration for some other component to limit the rate of haemoglobin synthesis, reticulocyte and oocyte factors altered the pattern of protein synthesis only slightly in favour of haemoglobin and oocyte proteins, respectively.