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dictyNews Volume 25 Number 14
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.
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Abstracts
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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]
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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]
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[End dictyNews, volume 25, number 14] 
