Dynamics of native β-actin mRNA transport in the cytoplasm

Transport of mRNAs in the cytoplasm is essential for localization to translation sites and for post-transcriptional regulation. Utilizing single-RNA sensitive probes and real-time fluorescence microscopy, we accurately quantified the dynamics of native, non-engineered, β-actin mRNAs within the cytoplasm of epithelial cells and fibroblasts for the first time. Using single particle tracking and temporal analysis, we determined that native β-actin mRNAs, under physiologic conditions, exhibit bursts of intermittent, processive motion on microtubules, interspersed between time periods of diffusive motion, characterized by non-thermal enhanced diffusivity. When transport processes were perturbed via ATP-depletion, temperature reduction, dynamitin overexpression, and chemical inhibitors, processive motion was diminished or eliminated and diffusivity was reduced. These data support a model whereby processive, motor driven motion is responsible for long distance mRNA transport