title: The Scd6/Lsm14 protein xRAPB has properties different from RAP55 in selecting mRNA for early translation or intracellular distribution in Xenopus oocytes.
abstract: 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/Lsm14 proteins, typified by RAP55, function in a wide range of eukaryotes in repressing translation and relocating mRNPs to processing bodies and stress granules. In Xenopus laevis, the RAP55 orthologue xRAPA fulfils these functions. Here we describe the properties of a variant of xRAPA, xRAPB, which is a member of the Lsm14B group. xRAPB differs from xRAPA in various respects: it is expressed at high concentration earlier in oogenesis; it interacts specifically with the DDX6 helicase Xp54; it is detected in polysomes and stalled translation initiation complexes; its over-expression leads to selective binding to translatable mRNA species without evidence of translation repression or mRNA degradation. Since both Xp54 and xRAPA are repressors of translation, activation appears to be effected through targeting of xRAPB/Xp54.
authors.affiliation: Biomedical Sciences Research Complex, Biomolecular Sciences Building, University of St Andrews, North Haugh, St Andrews KY16 9TS, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Ladomery
authors.affiliation: Biomedical Sciences Research Complex, Biomolecular Sciences Building, University of St Andrews, North Haugh, St Andrews KY16 9TS, UK. Electronic address: js15@st-and.ac.uk.
authors.forename: John
authors.initials: J
authors.lastname: Sommerville
mesh_terms: D000818:Animals; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D011132:Polyribosomes / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: C516955:RAP55 protein, Xenopus; D012333:RNA, Messenger; D012097:Repressor Proteins; D029867:Xenopus Proteins; C486437:Xp54 RNA helicase, Xenopus; D053487:DEAD-box RNA Helicases
keywords: LSM14B‐A; Messenger ribonucleoprotein particles (mRNPs); Post-transcripional control; Scd6/RAP55 proteins; Xenopus oogenesis; Xp54/DDX6 helicase