At all steps from transcription to translation, RNA-binding proteins play important roles in determining mRNA
function. Initially it was believed that for the vast majority of transcripts the role of RNA-binding proteins is limited to
general functions such as splicing and translation. However, work from recent years showed that members of this class of
proteins also recognize several mRNAs via cis-acting elements for their incorporation into large motor-containing particles.
These particles are transported to distant subcellular sites, where they become subsequently translated. This process,
called mRNA localization, occurs along microtubules or actin filaments, and involves kinesins, dyneins, as well as myosins.
Although mRNA localization has been detected in a large number of organisms from fungi to humans, the underlying
molecular machineries are not well understood. In this review we will outline general principles of mRNA localization
and highlight three examples, for which a comparably large body of information is available. The first example is
She2p/She3p-dependent localization of ASH1 mRNA in budding yeast. It is particularly well suited to highlight the interdependence
between different steps of mRNA localization. The second example is Staufen-dependent localization of
oskar mRNA in the Drosophila embryo, for which the importance of nuclear events for cytoplasmic localization and
translational control has been clearly demonstrated. The third example summarizes Egalitarian/Bicaudal D-dependent
mRNA transport events in the oocyte and embryo of Drosophila. We will highlight general themes and differences, point
to similarities in other model systems, and raise open questions that might be answered in the coming years.
Keywords: ASH1 mRNA, cytoskeleton, K10 mRNA, motor proteins, mRNA localization, oskar mRNA, RNA-binding proteins,
translational control, posttranscriptional, mRNA.
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