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dictyNews Volume 29 Number 01
dictyNews
Electronic Edition
Volume 29, number 1
July 6, 2007
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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The localization of INCENP at the cleavage furrow is dependent on Kif12 and
involves interactions of the N-terminus of INCENP with the actin cytoskeleton.
Qian Chen1, Gandikota S. Lakshmikanth2, James A. Spudich2, and
Arturo De Lozanne1
1Section of Molecular Cell & Developmental Biology and Institute for Cellular
and Molecular Biology, University of Texas at Austin, Austin, TX 78712.
2Department of Biochemistry, Stanford University School of Medicine, Stanford,
CA 94305
Molecular Biology of the Cell, in press
The Inner Centromeric Protein (INCENP) and other chromosomal passenger
proteins are known to localize on the cleavage furrow and to play a role in
cytokinesis. However, it is not known how INCENP localizes on the furrow or
whether this localization is separable from that at the midbody. Here we
show that the association of DdINCENP with the cortex of the cleavage furrow
involves interactions with the actin cytoskeleton and depends on the presence
of the kinesin-6-related protein Kif12. We found that Kif12 is found on the
central spindle and the cleavage furrow during cytokinesis. Kif12 is not
required for the redistribution of DdINCENP from centromeres to the central
spindle. However, in the absence of Kif12, DdINCENP fails to localize on the
cleavage furrow. Domain analysis indicates that the Nterminus of DdINCENP is
necessary and sufficient for furrow localization and binds directly to the
actin cytoskeleton. Our data suggest that INCENP moves from the central
spindle to the furrow of a dividing cell by a Kif12 dependent pathway. Once
INCENP reaches theequatorial cortex it associates with the actin cytoskeleton
where it then concentrates toward the end of cytokinesis.
Submitted by: Arturo De Lozanne [a.delozanne@mail.utexas.edu]
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Prolyl 4-hydroxylase-1 mediates O2-signaling during development of
Dictyostelium
Christopher M. West, Hanke van der Wel and Zhuo A. Wang
Department of Biochemistry & Molecular Biology and the Oklahoma Center for
Medical Glycobiology, University of Oklahoma Health Sciences Center,
Oklahoma City, OK, 73104 USA
Development, in press
Development in multicellular organisms is subject to both environmental and
internal signals. In Dictyostelium, starvation induces amoebae to form migratory
slugs that translocate from subterranean to exposed sites where they culminate
to form sessile fruiting bodies. Culmination, thought to be regulated by anterior
tip cells, is selectively suppressed by mild hypoxia by a mechanism that can
be partially overridden by another environmental signal, overhead light, or
genetic activation of protein kinase A. Dictyostelium expresses, in all cells,
an O2-dependent prolyl 4-hydroxylase (P4H1) required for O-glycosylation of Skp1,
a subunit of E3SCF-Ub-ligases. P4H1-null cells differentiate the basic prestalk
and prespore cell types, but exhibit a selectively increased O2-requirement for
culmination from ~12% to near or above ambient (21%) levels. Overexpression of
P4H1 reduces the O2 requirement to <5%. The requirement for P4H1 can be met by
forced expression of the active enzyme in either prestalk (anterior) or prespore
(posterior) cells, or replaced by protein kinase A activation or addition of
small numbers of wild-type cells. P4H1-expressing cells accumulate at the
anterior end, suggesting that P4H1 enables transcellular signaling by the tip.
The evidence provides novel genetic support for the animal-derived O2-sensor
model of prolyl 4-hydroxylase function, in an organism that lacks the canonical
HIF? transcriptional factor subunit substrate target that is a feature of animal
hypoxic signaling.
Submitted by: Chris West [Cwest2@ouhsc.edu]
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[End dictyNews, volume 29, number 1]
