dictyNews
Electronic Edition
Volume 36, number 12
April 8, 2011
Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to [log in to unmask]
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
=========
Sequence and generation of mature ribosomal RNA transcripts in
Dictyostelium discoideum
Carsten Boesler1, Janis Kruse1, Fredrik Söderbom2, and
Christian Hammann1
1 Heisenberg Research Group Ribogenetics, Technical University of
Darmstadt, 64287 Darmstadt, Germany
2 Department of Molecular Biology, Uppsala Biomedical Center, Swedish
University of Agricultural Sciences, S-75124 Uppsala, Sweden
JBC, in press
The amoeba Dictyostelium discoideum is a well-established model organism
for studying numerous aspects of cellular and developmental functions. Its
ribosomal RNA (rRNA) is encoded in an extrachromosomal palindrome that
exists in ca. 100 copies in the cell. In this study, we have set out investigate
the sequence of the expressed rRNA. For this, we have ligated the rRNA
ends and performed RT-PCR on these circular RNAs. Sequencing revealed
that the mature 26S, 17S, 5.8S and 5S rRNAs have sizes of 3741, 1871, 162
and 112 nucleotides, respectively. Unlike published, all mature rRNAs of a
type uniformly display the same start and end nucleotides in the analyzed AX2
strain. We show the existence of a short-lived primary transcript covering the
rRNA transcription unit of 17S, 5.8S and 26S rRNA. Northern blots and RT-PCR
reveal that from this primary transcript two precursor molecules of the 17S and
two precursors of the 26S rRNA are generated. We have also determined the
sequences of these precursor molecules, and based on this data, we propose
a model for the maturation of the rRNAs in Dictyostelium discoideum that we
compare to the processing of the rRNA transcription unit of Saccharomyces
cerevisiae.
Submitted by Christian Hammann [[log in to unmask]]
--------------------------------------------------------------------------------
Genetically tagged TRE5-A retrotransposons reveal high amplification rates
and authentic target site preference in the Dictyostelium discoideum genome
Oliver Siol, Thomas Spaller, Jana Schiefner and Thomas Winckler
School of Biology and Pharmacy, Institute of Pharmacy, Department of
Pharmaceutical Biology, University of Jena, Semmelweisstrasse 10,
07743 Jena, Germany
Nucleic Acids Research, in press
Retrotransposons contribute significantly to the evolution of eukaryotic genomes.
They replicate by producing DNA copies of their own RNA, which are integrated
at new locations in the host cell genome. In the gene-dense genome of the
social amoeba Dictyostelium discoideum, retrotransposon TRE5-A avoids
insertional mutagenesis by targeting the transcription factor (TF) IIIC/IIIB complex
and integrating ~50 bp upstream of tRNA genes. We generated synthetic TRE5-A
retrotransposons (TRE5-Absr) that were tagged with a selection marker that
conferred resistance to blasticidin after a complete retrotransposition cycle. We
found that the TRE5-Absr elements were efficiently mobilized in trans by proteins
expressed from the endogenous TRE5-A population found in D. discoideum cells.
ORF1 protein translated from TRE5-Absr elements significantly enhanced
retrotransposition. We observed that the 5' untranslated region of TRE5-A could
be replaced by an unrelated promoter, whereas the 3' untranslated region of
TRE5-A was essential for retrotransposition. A predicted secondary structure in
the RNA of the 3' untranslated region of TRE5-A may be involved in the
retrotransposition process. The TRE5-Absr elements were capable of identifying
authentic integration targets in vivo, including formerly unnoticed, putative
binding sites for TFIIIC on the extrachromosomal DNA element that carries the
ribosomal RNA genes.
Submitted by Thomas Winckler [[log in to unmask]]
--------------------------------------------------------------------------------
The Role of Extracellular Cations in Cell Motility, Polarity and Chemotaxis
David R. Soll, Deborah Wessels, Daniel F. Lusche, Spencer Kuhl,
Amanda Scherer, and Shawna Grimm
Research and Reports in Biology
http://www.dovepress.com/articles.php?article_id=7033
The concentrations of cations in the aqueous environment of free living organisms
and cells within the human body influence motility, shape and chemotaxis. The
role of extracellular cations is usually perceived to be the source for intracellular
cations in the process of homeostasis. The role of surface molecules that interact
with extracellular cations is believed to be that of channels, transporters and
exchangers. However, the role of Ca++ as a signal and chemoattractant, and
the discovery of the Ca++ receptor CaR, have demonstrated that extracellular
cations can function as signals at the cell surface, and the plasma membrane
molecules they interact with can function as bona fide receptors that activate
coupled signal transduction pathways, associated molecules in the plasma
membrane or the cytoskeleton. With this perspective in mind, we have reviewed
the cationic composition of aqueous environments of free living cells and cells that
move in multicellular organisms, most notably humans, the range of molecules
interacting with cations at the cell surface, the concept of a cell surface cation
receptor, and the roles extracellular cations and the plasma membrane proteins
that interact with them play in the regulation of motility, shape and chemotaxis.
Hopefully, the perspective of this review will increase awareness of the roles
extracellular cations play and the possibility that many of the plasma membrane
proteins that interact with them could also play roles as receptors.
Submitted by Wessels Deborah [[log in to unmask]]
==============================================================
[End dictyNews, volume 36, number 12]
|
