dictyNews Electronic Edition Volume 41, number 21 October 2, 2015 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= A Derivative of Differentiation-inducing Factor-3 Inhibits PAK1 Activity and Breast Cancer Cell Proliferation Peter Oladimeji, Yuzuru Kubohara, Haruhisa Kikuchi, Yoshiteru Oshima, Courtney Rusch, Rebekah Skerl, & Maria Diakonova # # Corresponding Author. The Department of Biological Sciences, University of Toledo, Ohio, USA 43606-3390 Accepted for publication in Int. J. Cancer Clin. Res. Differentiation-inducing factors 1-3 (DIFs 1-3), chlorinated alkylphenones identified in the cellular slime mold Dictyostelium discoideum, are considered anti-tumor agents because they inhibit proliferation of a variety of mammalian tumor cells in vitro. Although the anti-proliferative effects of DIF-1 and DIF-3 are well-documented, the precise molecular mechanisms underlying the actions of DIFs have not been fully elucidated. In this study, we examined the effects of DIFs and their derivatives on PAK1, a key serine-threonine kinase, which is activated by multiple ligands and regulates cell proliferation. We examined the effect of DIF derivatives on PAK1 kinase activity in cells. We also examined the effect of DIF-3(+1) derivative on PAK1 kinase activity in vitro, cyclin D1 promoter activity and breast cancer cell proliferation. It was found that some derivatives strongly inhibited PAK1 kinase activity in human breast cancer MCF-7 cells stably overexpressing PAK1. Among the derivatives, DIF-3(+1) was most potent, which directly inhibited kinase activity of recombinant purified PAK1 in an in vitro kinase assay. Furthermore, DIF-3(+1) strongly inhibited both cyclin D1 promoter activity and proliferation of MCF-7 and T47D breast cancer cells stably overexpressing PAK1 in response to prolactin, estrogen, epidermal growth factor and heregulin. In the present study we propose PAK1 as DIF-3(+1) target mediating its anti-proliferative effect. Submitted by Yuzuru Kubohara [ykuboha@juntendo.ac.jp] ———————————————————————————————————— Dynamic modulation of Dnmt2-dependent tRNA methylation by the micronutrient queuine Martin Müller1, Mark Hartmann2, Isabelle Schuster3, Sebastian Bender2, Kathrin L. Thüring4, Mark Helm4, Jon R. Katze5, Wolfgang Nellen3, Frank Lyko2 and Ann E. Ehrenhofer-Murray1* 1 Institut für Biologie, Humboldt-Universität zu Berlin, 10115 Berlin, Germany 2 Division of Epigenetics, DKFZ-ZMBH Alliance, German Cancer Research Center, 69120 Heidelberg, Germany 3 Abteilung für Genetik, Universität Kassel, 34132 Kassel, Germany 4 Institut für Pharmakologie und Biochemie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany 5 Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, TN 38163, USA accepted: Nucleic Acids Res. ABSTRACT Dnmt2 enzymes are cytosine-5 methyltransferases that methylate C38 of several tRNAs. We report here that the activities of two Dnmt2 homologs, Pmt1 from Schizosaccharomyces pombe and DnmA from Dictyostelium discoideum, are strongly stimulated by prior queuosine (Q) modification of the substrate tRNA. In vivo tRNA methylation levels were stimulated by growth of cells in queuine-containing medium; in vitro Pmt1 activity was enhanced on Q-containing RNA; and queuine-stimulated in vivo methylation was abrogated by the absence of the enzyme that inserts queuine into tRNA, eukaryotic tRNA-guanine transglycosylase. Global analysis of tRNA methylation in S. pombe showed a striking selectivity of Pmt1 for tRNAAsp methylation, which distinguishes Pmt1 from other Dnmt2 homologs. The present analysis also revealed a novel Pmt1- and Q-independent tRNA methylation site in S. pombe, C34 of tRNAPro. Notably, queuine is a micronutrient that is scavenged by higher eukaryotes from the diet and gut microflora. This work therefore reveals an unanticipated route by which the environment can modulate tRNA modification in an organism. Submitted by Wolfgang Nellen [nellen@uni-kassel.de] ——————————————————————————————————————— A resilient formin-derived cortical actin meshwork in the rear drives actomyosin-based motility in 2D confinement Nagendran Ramalingam1,2,*, Christof Franke 3,*, Evelin Jaschinski 4, Moritz Winterhoff 3, Yao Lu 5, Stefan Brühmann 3, Alexander Junemann 3, Helena Meier 3, Angelika A. Noegel 6, Igor Weber 7, Hongxia Zhao 5, Rudolf Merkel 4, Michael Schleicher 1, and Jan Faix 3 * These authors contributed equally to this work 1 Anatomy III/Cell Biology, BioMedCenter, Ludwig-Maximilians-University, Grosshaderner Str. 9, Planegg-Martinsried, Germany; 2 present address: Department of Neurology, Columbia University, 650 West 168th Street, New York, NY 10032, USA; 3 Institute for Biophysical Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany; 4 Instituteof Complex Systems, ICS-7: Biomechanics, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; 5 Institute of Biotechnology, PO Box 56, University of Helsinki, Helsinki 00014, Finland; 6 Center for Biochemistry, Medical Faculty, University of Cologne, 50931 Köln, Germany; 7 Division of Molecular Biology, Ruder Boškovic; Institute, Bijenicka 54, 10000 Zagreb, Croatia. Nature Communications, in press Cell migration is driven by the establishment of disparity between the cortical properties ofthe softer front and the more rigid rear allowing front extension and actomyosin-based rearcontraction. However, how the cortical actin meshwork in the rear is generated remains elusive. Here we identify the mDia1-like formin A (ForA) from Dictyostelium discoideum that generates a subset of filaments as the basis of a resilient cortical actin sheath in the rear. Mechanical resistance of this actin compartment is accomplished by actin crosslinkers and IQGAP-related proteins, and is mandatory to withstand the increased contractile forces in response to mechanical stress by impeding unproductive blebbing in the rear, allowing efficient cell migration in two-dimensional-confined environments. Consistently, ForA supresses the formation of lateral protrusions, rapidly relocalizes to new prospective ends in repolarizing cells and is required for cortical integrity. Finally, we show that ForA utilizes the phosphoinositide gradients in polarized cells for subcellular targeting. Submitted by Jan Faix [faix.jan@mh-hannover.de] ============================================================== [End dictyNews, volume 41, number 21]