Tropomyosin synthesis accompanies formation of actin filaments in embryonal carcinoma cells induced to differentiate by hexamethylene bisacetamide.

Abstract
Hexamethylene bisacetamide (HMBA) induces in vitro the cytodifferentiation of PCC3/A/1 mouse embryonal carcinoma (EC) cells. In EC cells, actin is associated with surface structures but microfilament bundles are not seen. After 2 days of HMBA treatment, rounded EC cells are converted to flat adhesive ones with a developed cytoskeleton containing actin and tropomyosin. The ratio of actin to total proteins is constant in EC cells and their HMBA derivatives; but a striking difference is observed for 1 of the newly synthesized proteins (MW 34,000) identified as tropomyosin. Synthesis of tropomyosin is followed by its association with actin microfilament bundles, as revealed by indirect immunofluorescence microscopy with specific antibodies.