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dictyNews Volume 43 Number 01
dictyNews
Electronic Edition
Volume 43, number 1
January 13, 2017
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.
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HAPPY NEW YEAR!
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Abstracts
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Early nucleolar disorganization in Dictyostelium cell death
MF Luciani, Y Song, A Sahrane, A Kosta, P Golstein
Cell Death and Disease, in press
Cell death occurs in all eukaryotes, but it is still not known
whether some core steps of the cell death process are conserved.
We investigated this using the protist Dictyostelium. The dissection
of events in Dictyostelium vacuolar developmental cell death was
facilitated by the sequential requirement for two distinct exogenous
signals. An initial exogenous signal (starvation and cAMP) recruited
most cells into clumps. Only within these clumps did subsequent
cell death events take place. Contrary to our expectations, already
this initial signal provoked nucleolar disorganization and irreversible
inhibition of rRNA and DNA synthesis, reflecting marked cell
dysfunction. The initial signal also primed clumped cells to respond
to a second exogenous signal (DIF-1 or c-di-GMP), which led to
vacuolization and synthesis of cellulose encasings. Thus, the latter
prominent hallmarks of developmental cell death were induced
separately from initial cell dysfunction. We propose that (1) in
Dictyostelium vacuolization and cellulose encasings are late,
organism-specific, hallmarks, and (2) on the basis of our observations
in this protist and of similar previous observations in some cases of
mammalian cell death, early inhibition of rRNA synthesis and nucleolar
disorganization may be conserved in some eukaryotes to usher in
developmental cell death.
submitted by: Pierre Golstein [golstein@ciml.univ-mrs.fr]
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CP39, CP75 and CP91 are major structural components of the
Dictyostelium centrosome's core structure
Irene Meyer, Tatjana Peter, Petros Batsios, Oliver Kuhnert,
Anne Krüger-Genge, Carl Camurça, Ralph Gräf
University of Potsdam
Eur. J. Cell Biol., in press
The acentriolar Dictyostelium centrosome is a nucleus-associated
body consisting of a core structure with three plaque-like layers,
which are surrounded by a microtubule-nucleating corona. The core
duplicates once per cell cycle at the G2/M transition, whereby its
central layer disappears and the two outer layers form the mitotic
spindle poles. Through proteomic analysis of isolated centrosomes
we have identified CP39 and CP75, two essential components of the
core structure. Both proteins can be assigned to the central core
layer as their centrosomal presence is correlated to the disappearance
and reappearance of the central core layer in the course of centrosome
duplication. Both proteins contain centrosomal targeting domains in
their N- and C-terminal halves whereby the N-terminal half is required
for cell cycle-dependent regulation. CP39 is capable of self-interaction
and overexpression of GFP- CP39 elicits supernumerary microtubule-
organizing centers and precentrosomal cytosolic clusters.
Underexpression stops cell growth and reverses the MTOC amplification
phenotype. Depletion of CP75 by RNAi also elicits supernumerary
MTOCs. In addition CP75RNAi affects correct chromosome segregation
and causes co-depletion of CP39 and CP91, another central core layer
component. CP39 and CP75 interact with each other directly in a yeast
two hybrid assay. Furthermore CP39, CP75 and CP91 mutually interact
in a proximity-dependent biotin identification (BioID) assay. Our data
indicate that these three proteins are all required for proper centrosome
biogenesis and make up the major structural components of core
structure's central layer.
submitted by: Ralf Gräf [rgraef@uni-potsdam.de]
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[End dictyNews, volume 43, number 1]
