title: A stimulatory role for the La-related protein 4B in translation.
abstract: La-related proteins (LARPs) belong to an evolutionarily conserved family of factors with predicted roles in RNA metabolism. Here, we have analyzed the cellular interactions and function of LARP4B, a thus far uncharacterized member of the LARP family. We show that LARP4B is a cytosolic protein that accumulates upon arsenite treatment in cellular stress granules. Biochemical experiments further uncovered an interaction of LARP4B with the cytosolic poly(A) binding protein 1 (PABPC1) and the receptor for activated C Kinase (RACK1), a component of the 40S ribosomal subunit. Under physiological conditions, LARP4B co-sedimented with polysomes in cellular extracts, suggesting a role in translation. In agreement with this notion, overexpression of LARP4B stimulated protein synthesis, whereas knockdown of the factor by RNA interference impaired translation of a large number of cellular mRNAs. In sum, we identified LARP4B as a stimulatory factor of translation. We speculate that LARP4B exerts its function by bridging mRNA factors of the 3' end with initiating ribosomes.
authors.affiliation: Department of Biochemistry, Theodor Boveri-Institute, University of Wuerzburg, Wuerzburg D-97074, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Schäffler
authors.forename: Kristina
authors.initials: K
authors.lastname: Schulz
authors.forename: Anja
authors.initials: A
authors.lastname: Hirmer
authors.forename: Julia
authors.initials: J
authors.lastname: Wiesner
authors.forename: Michael
authors.initials: M
authors.lastname: Grimm
authors.forename: Albert
authors.initials: A
authors.lastname: Sickmann
authors.forename: Utz
authors.initials: U
authors.lastname: Fischer
mesh_terms: D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000072200:Ku Autoantigen; D011132:Polyribosomes / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D054682:Ribosome Subunits, Small, Eukaryotic; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; D000072200:Ku Autoantigen