Putting mRNA in Its Place

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Science  06 Mar 2009:
Vol. 323, Issue 5919, pp. 1266-1267
DOI: 10.1126/science.323.5919.1266d

Many cell types, including epithelial cells and neurons, have structurally and functionally separate cytoplasmic compartments, which enable them to perform distinct functions. This cellular polarization can be established by blocking the immediate translation of some mRNAs, allocating them instead to specific locations in the cell. Translation can then be initiated as needed, thus ensuring that the proteins are synthesized only in the selected location at the required time. In neurons, mRNAs coding for synaptic proteins are transported to dendrites, where they are translated into proteins upon synaptic stimulation. Di Penta et al. have found that the factor LSm1, which has previously been shown to participate in the degradation of mRNAs, is involved. They identified a protein-mRNA complex containing LSm1 and the nuclear cap-binding protein CBP80, which recognizes the modified nucleotide that caps the 5′ end of the mRNA. The authors propose that this complex assembles in the nucleus, which would indicate that the mechanisms that regulate localized protein synthesis come into play soon after transcription, and in neurons this protein-mRNA complex was targeted to dendritic spines. These alternative functions for an mRNA degradation factor and a nuclear cap-binding protein in mRNA transport reveal molecular links between apparently diverse cellular processes. — HP*

  • *Helen Pickersgill is a locum editor in Science's editorial department.

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