The Journal of Cell Biology, Vol 77, 698-701, Copyright © 1978 by The Rockefeller University Press
Differences between nucleus and cytoplasm in the degree of actin polymerization
RW Rubin, L Goldstein and C Ko
For purposes of studying the degree of polymerization of actin in nuclei,
nuclei from 35S-labeled amoebas (Amoeba proteus) were transplanted into
unlabeled cells, which were immediately lysed and extracted under
conditions considered to stabilize preexisting fibrous actin. The
enucleated 35S-donor cells were similarly treated for analysis of
cytoplasmic actin. The extraction conditions permitted separation of
soluble (unpolymerized or G) actin from pelletable (polymerized or F)
actin, and the radioactivity of each was determined after the actin was
separated from other proteins by polyacrylamide gel electrophoresis. We
found that about 2/3 of the actin within the nucleus is pelletable, whereas
only about 1/3 of the cytoplasmic actin is pelletable. We speculate that
polymerized actin in the nucleus is involved in the condensation of
chromatin.
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