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dictyNews Volume 42 Number 18
dictyNews
Electronic Edition
Volume 42, number 18
July 22, 2016
Please submit abstracts of your papers as soon as they have been
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Abstracts
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The protein domains of the Dictyostelium microprocessor that are
required for correct subcellular localization and for microRNA
maturation
Janis Kruse, Doreen Meier, Fides Zenk, Maren Rehders,
Wolfgang Nellen, Christian Hammann
RNA Biology, in press
The maturation pathways of microRNAs (miRNAs) have been
delineated for plants and several animals, belonging to the
evolutionary supergroups of Archaeplastida and Opisthokonta,
respectively. Recently, we reported the discovery of the
microprocessor complex in Dictyostelium discoideum of the
Amoebozoa supergroup. The complex is composed of the Dicer
DrnB and the dsRBD (double-stranded RNA binding domain)
containing protein RbdB. Both proteins localize at nucleoli, where
they physically interact, and both are required for miRNA maturation.
Here we show that the miRNA phenotype of a Delta-drnB gene
deletion strain can be rescued by ectopic expression of a series
of DrnB GFP fusion proteins, which consistently showed punctate
perinucleolar localization in fluorescence microscopy. These
punctate foci appear surprisingly stable, as they persist both
disintegration of nucleoli and degradation of cellular nucleic acids.
We observed that DrnB expression levels influence the number of
microprocessor foci and alter RbdB accumulation. An investigation
of DrnB variants revealed that its newly identified nuclear localization
signal is necessary, but not sufficient for the perinucleolar localization.
Biogenesis of miRNAs, which are RNA Pol II transcripts, is correlated
with that localization. Besides its bidentate RNase III domains, DrnB
contains only a dsRBD, which surprisingly is dispensable for miRNA
maturation. This dsRBD can, however, functionally replace the
homologous domain in RbdB. Based on the unique setup of the
Dictyostelium microprocessor with a subcellular localization
similar to plants, but a protein domain composition similar to
animals, we propose a model for the evolutionary origin of
RNase III proteins acting in miRNA maturation.
submitted by: Christian Hammann [c.hammann@jacobs-university.de]
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[End dictyNews, volume 42, number 18]
