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dictyNews Volume 21 Number 14
Dicty News
Electronic Edition
Volume 21, number 14
October 31, 2003
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 Dicty-News, the Dicty Reference database and other
useful information is available at dictyBase - http://dictybase.org.
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Abstracts
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A cAMP Receptor-like G Protein-coupled Receptor with Roles in Growth Regulation
and Development
Brent Raisley, Minghang Zhang, Dale Hereld, and Jeffrey A. Hadwiger
Developmental Biology, in press
Dictyostelium discoideum uses G protein-mediated signal transduction for many
vegetative and developmental functions, suggesting the existence of G
protein-coupled receptors (GPCRs) other than the four known cAMP receptors
(cAR1-4). ÊSequences of the cAMP receptors were used to identify Dictyostelium
genes encoding cAMP receptor-like proteins, CrlA-C. ÊLimited sequence identity
between these putative GPCRs and the cAMP receptors suggests the Crl receptors
are unlikely to be receptors for cAMP. ÊThe crl genes are expressed at various
times during growth and the developmental life cycle. ÊDisruption of individual
crl genes did not impair chemotactic responses to folic acid or cAMP or alter
cAMP-dependent aggregation. ÊHowever, crlA- mutants grew to a higher cell
density than did wild-type cells and high-copy-number crlA expression vectors
were detrimental to cell viability, suggesting that CrlA is a negativ! e
regulator of cell growth. In addition, crlA- mutants produce large aggregates
with delayed anterior tip formation indicating a role for the CrlA receptor
in the development of the anterior prestalk cell region. ÊThe scarcity of
GFP-expressing crlA- mutants in the anterior prestalk cell region of chimeric
organisms supports a cell-autonomous role for the CrlA receptor in prestalk
cell differentiation.
Ê
Submitted by: Jeff A Hadwiger [hadwige@okstate.edu]
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Template jumping by a Dictyostelium LINE reverse transcriptase created a
SINE-like 5S rRNA retropseudogene
Karol Szafranski(1), Theodor Dingermann(2), Gernot Gloeckner(1) and
Thomas Winckler(2)
1 IMB Jena, Department of Genome Analysis, Beutenbergstrasse 11,
D-07745 Jena, Germany
2 Institut fuer Pharmazeutische Biologie, Universitaet Frankfurt/M.
(Biozentrum), Marie-Curie-Strasse 9, D-60439 Frankfurt am Main, Germany
Molecular & General Genomics, in press
Short interspersed nuclear elements (SINEs) are nonautonomous retroelements
that mimick the 3' ends of fellow long interspersed nuclear elements (LINEs)
to ensure their propagation by autonomous LINE-encoded proteins. The
Dictyostelium discoideum genome contains a family of LINE-like retrotransposons
that specifically target tRNA genes for integration (TRE elements). We
discovered a retrotransposed ribosomal 5S RNA pseudogene in the D. discoideum
genome that contains at its 3' end eight nucleotides derived from a TRE 3' end
and a polyadenine tail. The r5S retropseudogene is flanked by target site
duplications characteristic for TREs and is inserted upstream of a tRNA gene,
the typical integration sites of TREs. The D. discoideum r5S retropseudogene has
structural features of a short interspersed nuclear element (SINE) but did not
amplify, probably due to the 5'-truncation that occured upon its very first
retrotransposition. The discovery of the D. discoideum r5S retropseudogene
reveals that SINEs can be created de novo during reverse transcription of
LINE transcripts if the LINE-encoded reverse transcriptase dissociates from the
LINE RNAs and jumps to other cellular RNAs, particularly genes transcribed by RNA
polymerase III, to create continuous mixed cDNAs.
Submitted by: Thomas Winckler [winckler@em.uni-frankfurt.de]
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[End Dicty News, volume 21, number 14]
