CSM News Electronic Edition Volume 6, number 10 April 13, 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 =========== Primary structure, expression, and developmental regulation of a Dictyostelium calcineurin A homologue Heike Dammann, Simon Hellstern, Qayyum Husain and Rupert Mutzel Fakultat fur Biologie, Universitat Konstanz, 78434 Konstanz, Germany Eur. J. Biochem., in press. Summary cDNA clones for the catalytic subunit of Ca2+/calmodulin-dependent protein phosphatase (calcineurin A, protein phosphatase 2B) from Dictyostelium discoideum were isolated by functional screening of a lambda gt11 lysogen expression library with labeled Dictyostelium calmodulin. A complete cDNA of 2146 base pairs predicts a protein of 623 amino acids with homology to calcineurin A from other organisms and a similar molecular architecture. However, the Dictyostelium protein contains N-terminal and C-terminal extra domains causing a significantly higher molecular mass than found in any of its known counterparts. Recombinant Dictyostelium calcineurin A was purified from E. coli cells and shown to display similar enzymatic properties as the enzyme from other sources. On Western blots specific antibodies against the protein recognized a band of ca. 80 kDa that comigrated with an endogenous CaM-binding activity. Both the mRNA for calcineurin A and the protein are expressed during the growth phase. During early development the abundancy of the protein is reduced and then increases to peak after 10 h of starvation, when tight aggregates have formed. --------------------------------------------------------------------- Apurinic/apyrimidinic (AP) endonuclease from Dictyostelium discoideum: Cloning, nucleotide sequence, and induction by sublethal levels of DNA damaging agents Thomas M. Freeland, Robert B. Guyer, Angela Z. Ling, and Reginald A. Deering Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA Nucleic Acids Research, in press ABSTRACT We have cloned an AP endonuclease gene (APEA), from Dictyostelium discoideum, along with 1.8 kb of the 5' flanking region. There are no introns. The sequence predicts a protein of 361 amino acids, showing high homology to the major human/E. coli exonuclease III family of AP endonucleases. There is 47% identity and 64% similarity to the Ape endonuclease of human cells using the C-terminal 257 amino acids of the Dictyostelium protein. The 104 amino acids on the N-terminus show only low homology with other AP endonucleases. Instead, this region shows high homology with the acid-rich regions of proteins associated with chromatin, such as nucleolins and HMG proteins. The gene is transcriptionally activated up to 7-fold after treatment of cells with sublethal levels of DNA damaging agents, including ultraviolet light, MMNG, and bleomycin. The induction does not occur following the blocking of replication-fork polymerases with aphidicolin. It is not eliminated by treatment with kinase or phosphatase inhibitors. Four DNA damage-sensitive mutants all retained the DNA damage induced upregulation. -------------------------------------------------------------------- [End CSM News, volume 6, number 10]