MASKING MESSENGER-RNA FROM TRANSLATION IN SOMATIC-CELLS

We present evidence for a role for Y-box proteins in both mRNA transcr iption and translation. We have expressed an oocyte-specific RNA-bindi ng protein (FRGY2) in somatic cells. This protein is normally found to gether with mRNA in large amounts within the masked maternal mRNA stor age particles of Xenopus laevis oocytes. Masked maternal mRNA is belie ved to be translationally repressed during oogenesis and is stored wit hin ribonucleoprotein storage particles for subsequent use during embr yogenesis. Surprisingly, FRGY2 is not only found to direct the accumul ation of mRNA from promoters containing binding sites for the protein but also to selectively repress translation of the same mRNA. Thus, th e role of FRGY2 in the transcription and storage of maternal mRNA is s imilar to that of the transcription factor TFIIIA in the transcription and storage of 5S rRNA from the oocyte type 5S rRNA genes.