title: Cytoplasmic foci are sites of mRNA decay in human cells.
abstract: Understanding gene expression control requires defining the molecular and cellular basis of mRNA turnover. We have previously shown that the human decapping factors hDcp2 and hDcp1a are concentrated in specific cytoplasmic structures. Here, we show that hCcr4, hDcp1b, hLsm, and rck/p54 proteins related to 5'-3' mRNA decay also localize to these structures, whereas DcpS, which is involved in cap nucleotide catabolism, is nuclear. Functional analysis using fluorescence resonance energy transfer revealed that hDcp1a and hDcp2 interact in vivo in these structures that were shown to differ from the previously described stress granules. Our data indicate that these new structures are dynamic, as they disappear when mRNA breakdown is abolished by treatment with inhibitors. Accumulation of poly(A)(+) RNA in these structures, after RNAi-mediated inactivation of the Xrn1 exonuclease, demonstrates that they represent active mRNA decay sites. The occurrence of 5'-3' mRNA decay in specific subcellular locations in human cells suggests that the cytoplasm of eukaryotic cells may be more organized than previously anticipated.
authors.affiliation: Equipe labellisée La Ligue, Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, Avenue de la Terrasse, 91198 Gif sur Yvette, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Cougot
authors.forename: Sylvie
authors.initials: S
authors.lastname: Babajko
authors.forename: Bertrand
authors.initials: B
authors.lastname: Séraphin
mesh_terms: D002451:Cell Compartmentation / Q000235:genetics*; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D053487:DEAD-box RNA Helicases; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D015388:Organelles / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects / Q000235:genetics; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012316:RNA Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism; D020871:RNA Stability / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054398:Receptors, CCR4; D019707:Receptors, Chemokine / Q000235:genetics / Q000378:metabolism
chemical_list: C515354:CCR4 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C090519:PTPRCAP protein, human; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D054398:Receptors, CCR4; D019707:Receptors, Chemokine; D012316:RNA Nucleotidyltransferases; D004722:Endoribonucleases; C489698:DCP1b protein, human; C467723:DCP2 protein, human; C485332:DcpS protein, human; C094683:DDX6 protein, human; D053487:DEAD-box RNA Helicases