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We
have analyzed intracellular distributions of mRNAs for the cytoskeletal
proteins actin, vimentin, and tubulin by in situ hybridization. Although
polyadenylated RNA was homogeneously distributed throughout the cell,
actin mRNA demonstrated a nonhomogeneous distribution in 95% of randomly
selected chicken embryonic myoblasts and fibroblasts, as detected by
isotopic and nonisotopic techniques. Actin mRNA concentrations were
highest at cell extremities, generally in lamellipodia, where grain
densities were up to 16-fold higher than in areas near the nucleus.
Vimentin mRNA, unlike actin mRNA, was distributed near the nucleus.
Tubulin mRNA appeared most concentrated in the peripheral cytoplasm.
These results demonstrate that cytoplasmic mRNAs are localized in specific,
nonrandom cellular patterns and that localized concentrations of specific
proteins may result from corresponding localization of their respective
mRNAs. Hence, actin mRNA distribution may result in increased concentration
of actin filaments in lamellipodia of motile cells. |
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