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-Actin Messenger RNA Localization and
Protein Synthesis Augment Cell Motility

* Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655; and In chicken embryo fibroblasts (CEFs),
Department
of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
-actin
mRNA localizes near an actin-rich region of cytoplasm
specialized for motility, the lamellipodia. This localization is mediated by isoform-specific 3
-untranslated
sequences (zipcodes) and can be inhibited by antizipcode oligodeoxynucleotides (ODNs) (Kislauskis, E.H.,
X.-C. Zhu, and R.H. Singer. 1994. J. Cell Biol. 127:
441-451). This inhibition of
-actin mRNA localization
resulted in the disruption of fibroblast polarity and,
presumably, cell motility. To investigate the role of
-actin mRNA in motility, we correlated time-lapse images of moving CEFs with the distribution of
-actin
mRNA in these cells. CEFs with localized
-actin
mRNA moved significantly further over the same time
period than did CEFs with nonlocalized mRNA. Antizipcode ODN treatment reduced this cell translocation
while control ODN treatments showed no effect. The
temporal relationship of
-actin mRNA localization to
cell translocation was investigated using serum addition
to serum-deprived cultures.
-actin mRNA was not localized in serum-deprived cells but became localized
within minutes after serum addition (Latham, V.M.,
E.H. Kislauskis, R.H. Singer, and A.F. Ross. 1994. J. Cell Biol. 126:1211-1219). Cell translocation increased
over the next 90 min, and actin synthesis likewise increased. Puromycin reduced this cell translocation and
blocked this induction in cytosolic actin content. The
serum induction of cell movement was also inhibited by
antizipcode ODNs. These observations support the hypothesis that
-actin mRNA localization and consequent protein synthesis augment cell motility.
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