Copy Link
Add to Bookmark
Report
dictyNews Volume 43 Number 24
dictyNews
Electronic Edition
Volume 43, number 24
October 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.
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
=========
Retrotransposon domestication and control in Dictyostelium discoideum
Marek Malicki, Maro Iliopoulou† and Christian Hammann
Ribogenetics Biochemistry Lab, Department of Life Sciences and
Chemistry, Jacobs University Bremen, Bremen, Germany
†present address: Wellcome Trust Centre for Human Genetics, University
of Oxford, Oxford, United Kingdom
Frontiers in Microbiology, in press
Transposable elements, identified in all eukaryotes, are mobile genetic
units that can change their genomic position. Transposons usually employ
an excision and reintegration mechanism, by which they change position,
but not copy number. In contrast, retrotransposons amplify via RNA
intermediates, increasing their genomic copy number. Hence, they
represent a particular threat to the structural and informational integrity of
the invaded genome. The social amoeba Dictyostelium discoideum,
model organism of the evolutionary Amoebozoa supergroup, features a
haploid, gene-dense genome that offers limited space for damage-free
transposition. Several of its contemporary retrotransposons display intrinsic
integration preferences, for example by inserting next to transfer RNAs
genes or other retroelements. Likely, any retrotransposons that invaded the
genome of the amoeba in a non-directed manner were lost during evolution,
as this would result in decreased fitness of the organism. Thus, the
positional preference of the Dictyostelium retroelements might represent a
domestication of the selfish elements. Likewise, the reduced danger of such
domesticated transposable elements led to their accumulation, and they
represent about 10% of the current genome of D. discoideum. To prevent
the uncontrolled spreading of retrotransposons, the amoeba employs control
mechanisms including RNA interference and heterochromatization. Here, we
review TRE5-A, DIRS-1 and Skipper-1, as representatives of the three
retrotransposon classes in D. discoideum, which make up 5.7 % of the
Dictyostelium genome. We compile open questions with respect to their
mobility and cellular regulation, and suggest strategies, how these questions
might be addressed experimentally.
submitted by: Christian Hammann [c.hammann@jacobs-university.de]
——————————————————————————————————————
The polymorphic proteins TgrB1 and TgrC1 function as a ligand-receptor
pair in Dictyostelium allorecognition
Shigenori Hirose, Gong Chen, Adam Kuspa and Gad Shaulsky
Baylor College of Medicine, Houston, TX
Journal of Cell Science, accepted
Allorecognition is a key factor in Dictyostelium development and sociality.
It is mediated by two polymorphic transmembrane proteins, TgrB1 and
TgrC1, that contain extracellular immunoglobulin domains. TgrB1 and
TgrC1 are necessary and sufficient for allorecognition and they carry out
separate albeit overlapping functions in development, but their mechanism
of action is unknown. Here we show that TgrB1 acts as a receptor and
TgrC1 as its ligand in cooperative aggregation and differentiation. The
proteins bind each other in a sequence-specific manner, TgrB1 exhibits a
cell-autonomous function, and TgrC1 acts non-cell-autonomously. The
TgrB1 cytoplasmic tail is essential for its function and it becomes
phosphorylated upon association with TgrC1. Dominant mutations in TgrB1
activate the receptor function and confer partial ligand independence.
These roles in development and sociality suggests that allorecognition is
critical in the integration of individual cells into a coherent organism.
submitted by: Gad Shaulsky [gadi@bcm.edu]
==============================================================
[End dictyNews, volume 43, number 24]
