De novo translation initiation on membrane-bound ribosomes as a mechanism for localization of cytosolic protein mRNAs to the endoplasmic reticulum.
RNA
; 20(10): 1489-98, 2014 Oct.
Article
en En
| MEDLINE
| ID: mdl-25142066
ABSTRACT
The specialized protein synthesis functions of the cytosol and endoplasmic reticulum compartments are conferred by the signal recognition particle (SRP) pathway, which directs the cotranslational trafficking of signal sequence-encoding mRNAs from the cytosol to the endoplasmic reticulum (ER). Although subcellular mRNA distributions largely mirror the binary pattern predicted by the SRP pathway model, studies in mammalian cells, yeast, and Drosophila have also demonstrated that cytosolic protein-encoding mRNAs are broadly represented on ER-bound ribosomes. A mechanism for such noncanonical mRNA localization remains, however, to be identified. Here, we examine the hypothesis that de novo translation initiation on ER-bound ribosomes serves as a mechanism for localizing cytosolic protein-encoding mRNAs to the ER. As a test of this hypothesis, we performed single molecule RNA fluorescence in situ hybridization studies of subcellular mRNA distributions and report that a substantial fraction of mRNAs encoding the cytosolic protein GAPDH resides in close proximity to the ER. Consistent with these data, analyses of subcellular mRNA and ribosome distributions in multiple cell lines demonstrated that cytosolic protein mRNA-ribosome distributions were strongly correlated, whereas signal sequence-encoding mRNA-ribosome distributions were divergent. Ribosome footprinting studies of ER-bound polysomes revealed a substantial initiation codon read density enrichment for cytosolic protein-encoding mRNAs. We also demonstrate that eukaryotic initiation factor 2α is bound to the ER via a salt-sensitive, ribosome-independent mechanism. Combined, these data support ER-localized translation initiation as a mechanism for mRNA recruitment to the ER.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Polirribosomas
/
Ribosomas
/
Biosíntesis de Proteínas
/
ARN Mensajero
/
Retículo Endoplásmico
Tipo de estudio:
Prognostic_studies
Límite:
Humans
Idioma:
En
Revista:
RNA
Asunto de la revista:
BIOLOGIA MOLECULAR
Año:
2014
Tipo del documento:
Article
País de afiliación:
Estados Unidos