dictyNews
Electronic Edition
Volume 46, number 17
June 19, 2020
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Abstracts
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Eukaryotic life without tQCUG: the role of Elongator-dependent tRNA
modifications in Dictyostelium discoideum
Manfred A. Schäck, Kim Philipp Jablonski, Stefan Gräf, Roland Klassen,
Raffael Schaffrath, Stefanie Kellner and Christian Hammann
Nucleic Acids Research, in press
In the Elongator-dependent modification pathway, chemical
modifications are introduced at the wobble uridines at position 34 in
transfer RNAs (tRNAs), which serve to optimize codon translation
rates. Here we show that this three-step modification pathway exists
in D. discoideum, model of the evolutionary superfamily Amoebozoa.
Not only are previously established modifications observable by mass
spectrometry in strains with the most conserved genes of each step
deleted, but also additional modifications are detected, indicating a
certain plasticity of the pathway in the amoeba. Unlike described for
yeast, D. discoideum allows for an unconditional deletion of the single
tQCUG gene, as long as the Elongator-dependent modification
pathway is intact. In gene deletion strains of the modification pathway,
protein amounts are significantly reduced as shown by flow cytometry
and Western blotting, using strains expressing different glutamine
leader constructs fused to GFP. Most dramatic are these effects,
when the tQCUG gene is deleted, or Elp3, the catalytic component of
the Elongator complex is missing. In addition, Elp3 is the most strongly
conserved protein of the modification pathway, as our phylogenetic
analysis reveals. The implications of this observation are discussed
with respect to the evolutionary age of the components acting in the
Elongator-dependent modification pathway..
submitted by: Christian Hammann [[log in to unmask]]
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Unilateral Cleavage Furrows in Multinucleate Cells
Julia Bindl, Eszter Sarolta Molnar, Mary Ecke, Jana Prassler,
Annette Müller-Taubenberger and Günther Gerisch
Published in Cells as part of the Special Issue Symmetry Breaking in
Cells and Tissues
Cells 2020, 9(6), 1493; https://doi.org/10.3390/cells9061493
Multinucleate cells can be produced in Dictyostelium by electric pulse-
induced fusion. In these cells, unilateral cleavage furrows are formed at
spaces between areas that are controlled by aster microtubules. A
peculiarity of unilateral cleavage furrows is their propensity to join laterally
with other furrows into rings to form constrictions. This means cytokinesis
is biphasic in multinucleate cells, the final abscission of daughter cells
being independent of the initial direction of furrow progression. Myosin-II
and the actin filament cross-linking protein cortexillin accumulate in
unilateral furrows, as they do in the normal cleavage furrows of
mononucleate cells. In a myosin-II-null background, multinucleate or
mononucleate cells were produced by cultivation either in suspension or
on an adhesive substrate. Myosin-II is not essential for cytokinesis either
in mononucleate or in multinucleate cells but stabilizes and confines the
position of the cleavage furrows. In fused wild-type cells, unilateral furrows
ingress with an average velocity of 1.7 µm × min-1, with no appreciable
decrease of velocity in the course of ingression. In multinucleate myosin-II-
null cells, some of the furrows stop growing, thus leaving space for the
extensive broadening of the few remaining furrows.
submitted by: Mary Ecke [[log in to unmask]]
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[End dictyNews, volume 46, number 17]
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