Study of Acidic Actin of Nuclear Skeleton

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1. The reactivity of three kinds of anti-actin antibodies with various kinds of actins were examined. The anti-enteric smooth muscle actin antibody reacted only with -cytoplasmic, enteric and aortic smooth muscle actins, while the anti-skeletal muscle actin serum reacted only with skeletal, cardiac and aortic smooth muscle actins. The monoclonal anti-actin antibody reacted with all types of actins. Based on these findings, acidic actins of mouse sarcoma 180 cells, of mouse melanoma B16 cells and of human cytochalasin-resistant KB cells were suggested to be related to -cytoplasmic actin.2. In vitro translated products of polyARNA from sarcoma 180 cells and from L5178Y cells were analyzed on two-dimensional gels. The acidic actin of sarcoma 180 cells was found to have its own mRNA, while that of L5178Y cells was suggested to be a post-translationally modified form of usual actins.3. An attempt to separate , and acidic actins without using SDS (hydroxyapatite, chromatofocusing, HPLC on ion-exchange resin・etc.)resultedin a poor success.4. A cDNA library was constructed from polyARNA of sarcoma 180 cells, and full length cDNA clones of -and -actins were obtained. However, cDNA clones of the acidic actin are not identified yet.5. In vitro RNA transport system using isolated nuclei of L5178Y cells was developed; phalloidin had no effect of the RNA transport.6. Cytochalasin had almost no effect on the DNA synthesis of malignant tumor cells, while it caused 80% decrease of DNA synthesis of benign tumor and normal cells.