Targeting of mRNAs to domains of the endoplasmic reticulum.

The targeting of proteins to specific regions of the cell by signal elements within the polypeptide sequence has received much attention, but proteins can also be directed to their appropriate cellular locations by localization of their mRNAs. This mechanism is seen clearly in polar cells like germ and embryonic cells, neurons and epithelia. Recent evidence indicates that mRNAs may also be localized to morphologically and functionally distinct endoplasmic reticulum membranes, thereby facilitating sorting of the proteins they encode to subdomains of the reticulum or to polarized plasma membranes.