Levels of filamentous and globular actin in Chinese hamster ovary cells throughout the cell cycle

Synchronous Chinese hamster ovary (CHO) cells were obtained by mitotic selection and the levels of globular (G) actin, filamentous (F) actin, and cytoskeletal-associated F-actin were determined as cells progressed through the cell cycle. Total actin levels remained quite constant when expressed as a percent of the total protein. An increase in F-actin occurred upon plating the mitotic cells, but this increase was shown to be a result of attachment to the substratum, since cells which remained attached during the second mitosis failed to show these changes. No large variation in the levels of either F-actin or cytoskeletal-associated F-actin occurred throughout the cell cycle. Therefore, changes in the morphology of the CHO cells which are accompanied by a reorganization of actin-containing microfilaments during the cell cycle are not accompanied by significant changes in the size of the monomeric actin pool.