The Scd6 protein xRAPB has properties different from RAP55 in selecting mRNA for early translation or intracellular distribution in Xenopus oocytes
BBA Gene Regulatory Mechanisms accepted BBAGRM-15-102R2 (2015) -
Authors: Ladomery M, Sommerville J
Oocytes accumulate mRNAs in the form of maternal ribonucleoprotein (RNP) particles, the protein components of which determine the location and stability of individual mRNAs prior to translation. Scd6 proteins, typified by RAP55, functions in a wide range of eukaryotes in repressing translation and relocating mRNPs to processing bodies and stress granules. Here we describe in Xenopus laevis a variant of RAP55, xRAPB, a member of the LSM14B family of proteins found in many other organisms, which also contains conserved Lsm and FDF domains but differs in containing fewer RGG repeats. xRAPB differs from xRAPA in other respects: it is expressed at high concentration earlier in oogenesis; it interacts specifically with the RNA helicase Xp54; it is a component of mRNP particles with a different size distribution; its over-expression leads to selective binding to translatable mRNA species without evidence of translation repression or mRNA degration. Since Xp54 is a dominant repressor of translation, activation appears to be effected by the dislocation of Xp54 from xRAPB.
Keywords: Messenger ribonucleoprotein particles (mRNPs); Scd6/RAP55 proteins; Dhh1/p54 helicase,post-transcripional control; Xenopus oogenesis