Dicty News Electronic Edition Volume 9, number 10 18 October 1997 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@nwu.edu. Back issues of Dicty-News, the Dicty Reference database and other useful information is available at the Dictyostelium Web Page "http://dicty.cmb.nwu.edu/dicty/dicty.html" ================== Faculty Position ================== The Division of Biological Sciences at the University of Missouri has a tenure track faculty position in CELL BIOLOGY at the assistant or associate professor level. Applicants should submit a CV, copies of reprints, and a statement of their research and teaching goals. In addition, the applicant should arrange to have three letters of reference submitted. Dr. John David Director Division of Biological Sciences 105 Tucker Hall University of Missouri Columbia, MO 65211 =========== Abstracts =========== BLOCKING THE ENDS OF TRANSFORMING DNA ENHANCES GENE TARGETING IN DICTYOSTELIUM. Nalini Shah-Mahoney, Tracy Hampton, Regina Vidaver, and David Ratner Department of Biology, Amherst College, Amherst, Mass., U.S.A. 01002. Gene, in press. Summary Eukaryotic gene replacement is often complicated by unwanted plasmid insertion events involving the ends of transforming DNA molecules. These undesirable and often multiple insertions occur both randomly (i. e., non-homologously) and at the targeted locus. By blocking the 3’ ends of transforming DNA with 2’3’ dideoxy- nucleotides, we have reduced the frequency of end-mediated DNA insertion in Dictyostelium amoebae. As a result, only one copy of the selectable gene is introduced at the target locus to achieve a precise gene disruption. ------------------------------------------------------------------------- The Dictyostelium discoideum b-1,4-mannosyltransferase gene, mntA, has two periods of developmental expression Sung-Keun Lee, Guochun Li, Sung-Lim Yu, Hannah Alexander and Stephen Alexander Division of Biological Sciences, University of Missouri, Columbia, MO 65211, USA Gene, in press Abstract The precise roles of protein glycosylation in multicellular development are poorly understood. We have characterized the mntA gene from Dictyostelium discoideum which encodes the b-1,4- mannosyltransferase enzyme that catalyzes the reaction: GDP-Man + dolichol-PP-GlcNAc2 ‘ dolichol-PP-GlcNAc2-Man + GDP. This gene has a central role in the synthesis of the lipid linked oligosaccharide precursor which becomes the core of all asparagine-linked (N-linked) glycans. The mntA gene contains a single small intron and encodes a 493 aa protein with a predicted molecular size of 56 kDa. It is located 5’ to the repE gene on chromosome IV and is transcribed in the opposite orientation to repE with which it shares a 585-bp of upstream intergenic region. The predicted mntA gene product shares 38% homology with the S. cerevisiae ALG1 gene product. The MntA protein has a region homologous to the putative dolichol-binding region in the yeast ALG1 protein, but it is located in a different part of the molecule. Northern analysis revealed that the expression of the mntA gene is regulated during multicellular development with two periods of mRNA accumulation. The mntA gene product has a classical endoplasmic reticulum retention motif, and is the first Dictyostelium gene encoding a protein that is active in this organelle. The identification of this gene will allow expanded studies of the role of N-linked glycans in multicellular development. ------------------------------------------------------------------------- [End Dicty News, volume 9, number 10]