dictyNews Electronic Edition Volume 40, number 14 June 6, 2014 Please submit abstracts of your papers as soon as they have been accepted for publication by by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit or by sending them to dicty@northwestern.edu 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 ========= Defects in the synthetic pathway prevent DIF-1 mediated stalk lineage specification cascade in the non-differentiating social amoeba, Acytostelium subglobosum. Mohri K, Hata T, Kikuchi H, Oshima Y, Urushihara H. Biology Open. Posted Online May 29, 2014 http://bio.biologists.org/content/early/2014/05/23/bio.20148359.long Separation of somatic cells from germ-line cells is a crucial event for multicellular organisms, but how this step was achieved during evolution remains elusive. In Dictyostelium discoideum and many other dictyostelid species, solitary amoebae gather and form a multicellular fruiting body in which germ-line spores and somatic stalk cells differentiate, whereas in Acytostelium subglobosum, acellular stalks form and all aggregated amoebae become spores. In this study, because most D. discoideum genes known to be required for stalk cell differentiation have homologs in A. subglobosum, we inferred functional variations in these genes and examined conservation of the stalk cell specification cascade of D. discoideum mediated by the polyketide differentiation-inducing factor-1 (DIF-1) in A. subglobosum. Through heterologous expression of A. subglobosum orthologs of DIF-1 biosynthesis genes in D. discoideum, we confirmed that two of the three genes were functional equivalents, while DIF-methyltransferase (As-dmtA) involved at the final step of DIF-1 synthesis was not. In fact, DIF-1 activity was undetectable in A. subglobosum lysates and amoebae of this species were not responsive to DIF-1, suggesting a lack of DIF-1 production in this species. On the other hand, the molecular function of an A. subglobosum ortholog of DIF-1 responsive transcription factor was equivalent with that of D. discoideum and inhibition of polyketide synthesis caused developmental arrest in A. subglobosum, which could not be rescued by DIF-1 addition. These results suggest that non-DIF-1 polyketide cascades involving downstream transcription factors are required for fruiting body development of A. subglobosum. Submitted by Hideko Urushihara [hideko@biol.tsukuba.ac.jp] --------------------------------------------------------------------------- Specific growth suppression of human cancer cells by targeted delivery of Dictyostelium mitochondrial ribosomal protein S4 Junji Chida1, Hikaru Araki2 and Yasuo Maeda3,* * Corresponding author: Yasuo Maeda kjygy352@ybb.ne.jp 1 Division of Molecular Neurobiology, Institute for Enzyme Research, The University of Tokushima, Kuramoto-cho, Tokushima 770-8503, Japan; E-mail: jchida@tokushima-u.ac.jp 2 Division of Enzyme Chemistry, Institute for Enzyme Research, The University of Tokushima, Kuramoto-cho, Tokushima 770-8503, Japan; E-mail: h1.arak108@gmail.com 3 Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan; E-mail: kjygy352@ybb.ne.jp Cancer Cell International, accepted Background In general, growth and differentiation are mutually exclusive but are cooperatively regulated throughout development. Thus, the process of a cellŐs switching from growth to differentiation is of great importance not only for the development of organisms but also for malignant transformation, in which this process is reversed. We have previously demonstrated using a Dictyostelium model system that the Dictyostelium mitochondrial ribosomal protein S4 (Dd-mrp4) gene expression is essential for the initiation of cell differentiation: Dd-mrp4-null cells fail to initiate differentiate, while the initial step of cell differentiation and the subsequent morphogenesis are markedly enhanced in mrp4OE cells overexpressing the Dd-mrp4 in the extramitochondrial cytoplasm. This raised a possibility that the ectopically enforced expression of the Dd-mrp4 in human cells might inhibit their growth, particularly of malignant tumor cells, by inducing cell differentiation. Methods Four kinds of human tumor cell lines were transfected by three kind of vector constructs (the empty vector: pcDNA3.1 (Mock); pcDNA3.1-rps4 bearing Dictyostelium cytoplasmic ribosomal protein S4; pcDNA3.1-mrp4 bearing Dictyostelium mitochondrial ribosomal protein S4). As controls, four kinds of human primary cultured cells were similarly transfected by the above vector constructs. After transfection, growth kinetics of cells was analyzed using cell viability assay, and also the TUNEL methods was used for evaluation of apoptotic cells. Results Ectopically expressed Dd-mrp4 suppressed cell proliferation through inducing apoptotic cell death specifically in the human lung adenocarcinoma (A549), epithelial cervical cancer (HeLa), hepatocellular carcinoma (HepG2) and colonic carcinoma (Caco-2), but not in primary cultured normal cells, such as human brain microvascular endothelial cells (HBMECs); human umbilical vein endothelial cells (HUVECs) and human normal hepatocytes (hHepsTM), with one exception (human cardiac fibloblasts (HCF). Conclusion The present finding that the ectopically enforced expression of Dd-mrp4 in human several tumor cell lines specifically suppresses their proliferation suggests strongly that the Dd-mrp4 gene derived from Dictyostelium mitochondria may provide a new promising therapeutic strategy for disrupting cell viability pathways in human cancers. Keywords: Mitochondrial ribosomal protein S4 (MRP4); Dd-mrp4; Anticancer action; Apoptosis; Proliferation; Differentiation; Human tumor; Dictyostelium discoideum Submitted by Yasuo Maeda [kjygy352@ybb.ne.jp] ============================================================== [End dictyNews, volume 40, number 14]