CSM News Electronic Edition Volume 7, number 12 November 2, 1996 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to CSM-News@worms.cmb.nwu.edu. Back issues of CSM-News, the CSM Reference database and other useful information is available by anonymous ftp from worms.cmb.nwu.edu [165.124.233.50], via Gopher at the same address, or by World Wide Web at the URL "http://worms.cmb.nwu.edu/dicty.html" =========== Abstracts =========== Antisense-mediated Regulation of Annexin VII Gene Expression during the Transition from Growth to Differentiation in Dictyostelium discoideum. Tatsuya Okafugi, Fumiyoshi Abe and Yasuo Maeda Gene, in press Summary Annexin VII is believed to be required for proper Ca2+-homeostasis in Dictyostelium discoideum cells. As was previously reported, the expression of Annexin VII gene increased during the transition of D. discoideum Ax-2 cells from growth to differentiation. We have casually cloned an interesting gene, Quit3, by the differential plaque hybridization. Quit3 had no coding region, and was expressed more predominantly in the growth phase than in the differentiation phase. Unexpectedly, this gene was found to encode the complementary sequence of Annexin VII. Therefore, it is most likely that Quit3 may regulate the Annexin VII synthesis by the natural antisense transcript via an antisense RNA-RNA interaction, thus resulting in striking increase of Annexin VII production in the phase-shift of cells from growth to differentiation. Since Annexin VII is known to be coded for by a single gene in Dictyostelium, the antisense RNA seemed to be encoded in the same genetic locus as the Annexin VII RNA. --------------------------------------------------------------------- Autophosphorylation of Dictyostelium myosin II heavy chain specific protein kinase C is required for its activation and membrane dissociation A. Dembinsky, H. Rubin and S. Ravid Department of Biochemistry, Hadassah Medical School, The Hebrew University Jerusalem 91120, Israel J. Biol. Chem., in press. SUMMARY Myosin II heavy chain (MHC) specific protein kinase C (MHC-PKC) isolated from the ameba, Dictyostelium discoideum, regulates myosin II assembly and localization in response to the chemoattractant cAMP. cAMP stimulation of Dictyostelium cells leads to translocation of MHC-PKC from the cytosol to the membrane fraction, as well as causing an increase in both MHC-PKC phosphorylation and its kinase activity. MHC-PKC undergoes autophosphorylation with each mole of kinase incorporating about 20 mole of phosphate. The MHC-PKC autophosphorylation sites are thought to be located within a domain at the COOH-terminal region of MHC-PKC which contains a cluster of 21 serine and threonine residues. Here we report that deletion of this domain, abolished the ability of the enzyme to undergo autophosphorylation in vitro. Furthermore, after this deletion, cAMP-dependent autophosphorylation of MHC-PKC, as well as cAMP-dependent increases in kinase activity and subcellular localization were also abolished. These results provide evidence for the role of autophosphorylation in the regulation of MHC-PKC and indicate that this MHC-PKC autophosphorylation is required for the kinase activation in response to cAMP and for subcellular localization. --------------------------------------------------------------------- [End CSM News, volume 7, number 12]