dictyNews Electronic Edition Volume 25, number 14 December 9, 2005 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. ============= Abstracts ============= bZIP Transcription Factor Interactions Regulate DIF Responses in Dictyostelium Eryong Huang1,2, Simone L. Blagg3, Thomas Keller3, Mariko Katoh2, Gad Shaulsky2,4 and Christopher R. L. Thompson3,4 1 Graduate Program in Structural Computational Biology and Molecular Biophysics 2 Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas, 77030, USA 3 Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester, M13 9PT, UK 4 Authors for correspondence Development, in press The signaling molecule DIF-1 is required for normal cell fate choice and patterning in Dictyostelium. To understand how these developmental processes are regulated will require knowledge of how cells receive and respond to the DIF-1 signal. Previously, we described a bZIP transcription factor, DimA, which is required for cells to respond to DIF-1. However, it was unknown whether DimA activity is required to activate the DIF response pathway in certain cells or is a component of the response pathway itself. In this study we describe the identification of a DimA related bZIP transcription factor, DimB. Rapid changes in the subcellular localisation of both DimA and DimB in response to DIF-1 suggest that they are directly downstream of the DIF-1 signal. Genetic and biochemical interactions between DimA and DimB provides evidence that their ability to regulate diverse targets in response to DIF-1 is partly due to their ability to form homo and heterodimeric complexes. DimA and DimB are therefore direct regulators of cellular responses to DIF-1. Submitted by: Chris Thompson [christopher.thompson@man.ac.uk] ----------------------------------------------------------------------------- The Dictyostelium bZIP transcription factor DimB regulates prestalk-specific gene expression Natasha V. Zhukovskaya*, Masashi Fukuzawa*, Yoko Yamada, Tsuyoshi Araki and Jeffrey G. Williams * Joint first authors University of Dundee, MSI/WTB Complex, Dow Street, Dundee DD1 5EH, UK. Development, in press The ecmA gene is specifically expressed in prestalk cells and its transcription is induced by the chlorinated hexaphenone DIF-1. We have purified a novel bZIP transcription factor, DimB, by affinity chromatography on two spatially separated ecmA promoter fragments. Mutagenesis of the cap-site proximal DimB-binding site (the –510 site) greatly decreases ecmA expression in the pstO cells, which comprise the rear half of the prestalk zone, and also in the Anterior-Like Cells, which lie scattered throughout the prespore region. However DimB is not essential for normal expression of the ecmA gene, instead it spatially limits its expression; ecmA is relatively highly expressed in the subset of prestalk cells that coats the prestalk zone but in slugs of a DimB-null strain, ecmA is highly expressed throughout the prestalk zone. Because the –510 site is required for correct ecmA expression, we posit a separate activator protein that competes with DimB for binding to the –510 site. DimB rapidly accumulates in the nucleus when cells are exposed to DIF-1, and ChIP analysis shows that, in the presence of extracellular cAMP, DIF-1 causes DimB to associate with the ecmA promoter in vivo. Thus, DIF-1 regulates DimB activity to generate a gradient of ecmA expression in the prestalk zone of the slug. Submitted by: Jeff Williams [j.g.williams@dundee.ac.uk] ============================================================================== [End dictyNews, volume 25, number 14]