title: Multiple binding of repressed mRNAs by the P-body protein Rck/p54.
abstract: Translational repression is achieved by protein complexes that typically bind 3' UTR mRNA motifs and interfere with the formation of the cap-dependent initiation complex, resulting in mRNPs with a closed-loop conformation. We demonstrate here that the human DEAD-box protein Rck/p54, which is a component of such complexes and central to P-body assembly, is in considerable molecular excess with respect to cellular mRNAs and enriched to a concentration of 0.5 mM in P-bodies, where it is organized in clusters. Accordingly, multiple binding of p54 proteins along mRNA molecules was detected in vivo. Consistently, the purified protein bound RNA with no sequence specificity and high nanomolar affinity. Moreover, bound RNA molecules had a relaxed conformation. While RNA binding was ATP independent, relaxing of bound RNA was dependent on ATP, though not on its hydrolysis. We propose that Rck/p54 recruitment by sequence-specific translational repressors leads to further binding of Rck/p54 along mRNA molecules, resulting in their masking, unwinding, and ultimately recruitment to P-bodies. Rck/p54 proteins located at the 5' extremity of mRNA can then recruit the decapping complex, thus coupling translational repression and mRNA degradation.
authors: UPMC Univ Paris 06, CNRS-FRE 3402, 75252 Paris cedex 5, France.
authors: Michèle
authors: M
authors: Ernoult-Lange
authors: Sonia
authors: S
authors: Baconnais
authors: Maryannick
authors: M
authors: Harper
authors: Nicola
authors: N
authors: Minshall
authors: Sylvie
authors: S
authors: Souquere
authors: Thomas
authors: T
authors: Boudier
authors: Marianne
authors: M
authors: Bénard
authors: Philippe
authors: P
authors: Andrey
authors: Gérard
authors: G
authors: Pierron
authors: Michel
authors: M
authors: Kress
authors: Nancy
authors: N
authors: Standart
authors: Eric
authors: E
authors: le Cam
authors: Dominique
authors: D
authors: Weil
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*
chemical_list: D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D000255:Adenosine Triphosphate; C094683:DDX6 protein, human; D053487:DEAD-box RNA Helicases