For some types of cells, notably polarized cells, the localization of a protein can be regulated through mRNAs. mRNAs are transcribed from DNA, and then later translated into the proteins that function throughout the cell. By transporting mRNAs to specific regions, the cell in turn can have localized levels of proteins. A recent paper shows the specific localization of an mRNA encoding the signaling molecule MKK7 to neuronal growth cones, which are dynamic extension of a developing axon searching for its final target. According to Feltrin and colleagues, this localization of MKK7 mRNA may result in localized levels of MKK7 protein. MKK7 mRNA localization modulates JNK signaling, which in turn regulates microtubule bundling during neuronal outgrowth. In the images above, cells with reduced levels of MKK7 mRNA (bottom) have curled and bent microtubules (red in merged, black in right panels), compared to control cells (top).
Daniel Feltrin, Ludovico Fusco, Harald Witte, Francesca Moretti, Katrin Martin, Michel Letzelter, Erika Fluri, Peter Scheiffele, & Olivier Pertz (2012). Growth Cone MKK7 mRNA Targeting Regulates MAP1b-Dependent Microtubule Bundling to Control Neurite Elongation PLOS Bio, 10 (12) : 10.1371/journal.pbio.1001439