dictyNews Electronic Edition Volume 42, number 21 September 9, 2016 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 ========= Convergent evolution of tRNA gene targeting preferences in compact genomes Thomas Spaller1, Eva Kling1, Gernot Glöckner2,3, Falk Hillmann4, Thomas Winckler1 1 Institute of Pharmacy, Department of Pharmaceutical Biology, Friedrich Schiller University Jena, Germany 2 Institute for Biochemistry I, Medical Faculty, University of Cologne, Germany 3 Institute for Freshwater Ecology and Inland Fisheries, IGB, Berlin, Germany 4 Junior Research Group Evolution of Microbial Interaction, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute, Jena, Germany Mobile DNA, in press Background: In gene-dense genomes, mobile elements are confronted with highly selective pressure to amplify without causing excessive damage to the host. The targeting of tRNA genes as potentially safe integration sites has been developed by retrotransposons in various organisms such as the social amoeba Dictyostelium discoideum and the yeast Saccharomyces cerevisiae. In D. discoideum, tRNA gene- targeting retrotransposons have expanded to approximately 3% of the genome. Recently obtained genome sequences of species representing the evolutionary history of social amoebae enabled us to determine whether the targeting of tRNA genes is a generally successful strategy for mobile elements to colonize compact genomes. Results: During the evolution of dictyostelids, different retrotransposon types independently developed the targeting of tRNA genes at least six times. DGLT-A elements are long terminal repeat (LTR) retrotransposons that display integration preferences ~15 bp upstream of tRNA gene-coding regions reminiscent of the yeast Ty3 element. Skipper elements are chromoviruses that have developed two subgroups: one has canonical chromo domains that may favor integration in centromeric regions, whereas the other has diverged chromo domains and is found ~100 bp downstream of tRNA genes. The integration of D. discoideum non-LTR retrotransposons ~50 bp upstream (TRE5 elements) and ~100 bp downstream (TRE3 elements) of tRNA genes, respectively, likely emerged at the root of dictyostelid evolution. We identified two novel non-LTR retrotransposons unrelated to TREs: one with a TRE5-like integration behavior and the other with preference ~4 bp upstream of tRNA genes. Conclusions: Dictyostelid retrotransposons demonstrate convergent evolution of tRNA gene targeting as a probable means to colonize the compact genomes of their hosts without being excessively mutagenic. However, high copy numbers of tRNA gene-associated retrotransposons, such as those observed in D. discoideum, are an exception, suggesting that the targeting of tRNA genes does not necessarily favor the amplification of position-specific integrating elements to high copy numbers under the repressive conditions that prevail in most host cells. submitted by: Thomas Winckler [t.winckler@uni-jena.de] ——————————————————————————————————————— Identification of brefelamide as a novel inhibitor of osteopontin that suppresses invasion of A549 lung cancer cells Jing Zhang, Osamu Yamada, Shinya Kida, Yoshihisa Matsushita, Shinya Murase, Toshio Hattori, Yuzuru Kubohara, Haruhisa Kikuchi and Yoshiteru Oshima Oncol. REP. 36: 2357-2364, 2016 The contribution of aberrant osteopontin (OPN) expression to tumor progression and metastasis has been documented in a wide spectrum of malignancies, and targeted inhibition of OPN has therefore emerged as an attractive strategy for cancer therapy. Transcription of OPN is regulated by various transcription factors, and our recently published study demonstrated that downregulation of OPN is an important event in the TGF-beta cytostatic program. We report here that brefelamide, isolated from Dictyostelium brefeldianum, exerts an inhibitory effect on OPN expression and function in A549 human lung carcinoma cells. The promoter, RNA, and protein levels of OPN were decreased in brefelamide-treated A549 cells, which was accompanied by reduced invasive ability in vitro. OPN inhibition by brefelamide was largely abrogated by disruption of a putative TGF-beta inhibitory element in the OPN promoter. Treatment with brefelamide induced Smad4 expression, and knockdown of Smad4 by RNA interference partially diminished the inhibitory effect of brefelamide on OPN. These results indicate that brefelamide inhibited OPN-mediated cell invasion through restoration of the OPN repression by TGF-beta /Smad signaling. Together with the reported antiproliferative property, our findings suggest that brefelamide might serve as a potential candidate for the development of a new antitumor and antimetastatic agent. submitted by: Haruhisa Kikuchi [hal@mail.pharm.tohoku.ac.jp] ——————————————————————————————————————— Aberrant adhesion impacts early development in a Dictyostelium model for juvenile neuronal ceroid lipofuscinosis Robert J. Huber1*, Michael A. Myre2† and Susan L. Cotman3† 1Department of Biology, Trent University, Peterborough, Ontario, Canada 2Department of Biological Sciences, University of Massachusetts Lowell, Lowell, Massachusetts, USA 3Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA †These authors contributed equally *Corresponding author Cell Adhesion & Migration, in press Neuronal ceroid lipofuscinosis (NCL), also known as Batten disease, refers to a group of severe neurodegenerative disorders that primarily affect children. The most common subtype of the disease is caused by loss-of-function mutations in CLN3, which is conserved across model species from yeast to human. The precise function of the CLN3 protein is not known, which has made targeted therapy development challenging. In the social amoeba Dictyostelium discoideum, loss of Cln3 causes aberrant mid-to-late stage multicellular development. In this study, we show that Cln3-deficiency causes aberrant adhesion and aggregation during the early stages of Dictyostelium development. cln3- cells form ~30% more multicellular aggregates that are comparatively smaller than those formed by wild-type cells. Loss of Cln3 delays aggregation, but has no significant effect on cell speed or cAMP-mediated chemotaxis. The aberrant aggregation of cln3- cells cannot be corrected by manual pulsing cells with cAMP. Moreover, there are no significant differences between wild-type and cln3- cells in the expression of genes linked to cAMP chemotaxis (e.g., adenylyl cyclase, acaA; the cAMP receptor, carA; cAMP phosphodiesterase, pdsA; g-protein alpha 9 subunit, gpaI). However, during this time in development, cln3- cells show reduced cell-substrate and cell-cell adhesion, which correlate with changes in the levels of the cell adhesion proteins CadA and CsaA. Specifically, loss of Cln3 decreases the intracellular level of CsaA and increases the amount of soluble CadA in conditioned media. Together, these results suggest that the aberrant aggregation of cln3- cells is due to reduced adhesion during the early stages of development. Revealing the molecular basis underlying this phenotype may provide fresh new insight into CLN3 function. submitted by: Robert Huber [roberthuber@trentu.ca] ============================================================== [End dictyNews, volume 42, number 21]