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Poster Full Abstracts - RNA Biology
Poster board number is above title. The first author is the presenter
348
809B
The regulation and function of microRNAs during the maternal-to-zygotic transition in
Drosophila
.
Shengbo Fu
1
, Chung-Yi Nien
1
, Hsiao-Lan Liang
1
,
Stephen Butcher
2
, John Manak
2
, Christine Rushlow
1
. 1) Department of Biology, New York University, New York, NY; 2) Department of Biology,
University of Iowa, Iowa City, IA.
The maternal-to-zygotic transition (MZT) is a conserved pivotal process in which the transcribed zygotic genome gradually replaces maternally loaded
products to control embryonic development. Previously, our lab identified Zelda as a key activator of the early zygotic genome during the MZT of
Drosophila
. Zelda binds specifically to CAGGTAG and related sites, which are over-represented in the upstream regions of early zygotic genes (ten Bosch
et al., 2006; De Renzis et al., 2007). By comparing the expression profiles of wild-type and
zelda
mutant embryos, we demonstrated that over 70% of the
early-expressed zygotic genes are down-regulated in
zelda
mutants, but also that many maternal transcripts are up-regulated. Moreover, expression of the
miR-309
cluster, the first
Drosophila
zygotic factor shown to be involved in maternal transcript degradation (Bushati et al, 2008), is eliminated in
zelda
mutants. More recently, we showed that Zelda binds to the enhancer region of
miR-309
(Nien et al., 2011). Together, these results hinted that Zelda can
function in maternal mRNA degradation by activating early zygotic microRNAs. To further study the activation and function of microRNAs during the
MZT, we examined the expression profiles of wild-type and
zelda
mutant embryos using whole genome tiling arrays, and validated several Zelda-regulated
microRNA candidates by
in situ
hybridization. Further analysis showed that several of these microRNAs are regulated by a complex transcriptional network.
Current studies that focus on the function of these early zygotic microRNAs during the MZT will be presented that demonstrate the significance of the
Zelda-microRNA-maternal mRNA network during the MZT.
810C
miRNA function in a stress response in Drosophila S2 cells.
Mamiko Isaji, Pei-Hsuan Wu, Richard Carthew. Molecular Biosciences, Northwestern
University, Evanston, IL.
Cells are always exposed to environmental stresses, for example, nutrient restriction, oxidative stress, physical stress and also viral infections. Cellular
stress responses are very dynamic for allowing cells to effectively counteract and survive. A novel class of genes, termed microRNAs (miRNAs), has
recently been implicated in the cellular stress response. However, the relationship between miRNA and stress responses is just beginning to be explored.
Accumulating evidences show that the stress conditions can alter the miRNA biogenesis, expression of mRNA targets and the activities of miRNA-protein
complexes. In many of these cases, the molecular mechanism has been unclear and need to be investigated further to elucidate these fundamental roles of
miRNAs in controlling mRNA regulation during stress. How does stress regulate miRNA activities and how do cells mediate stress responses through
miRNAs? For understanding of this question, we observed Ago1-associated-complexes in cell fractionation by density gradient centrifugation in Drosophila
S2 cells under serum deprived condition. The Ago1-associated-complexes enriched at lower density fractions under the normal condition, however, under
serum deprivation, their enrichment has shifted to higher density fractions, and most of them were observed into the highest fraction which contains
abundant membrane structures including endoplasmic reticulum. Moreover, we tried to see the activity of the Ago1-associated-complexes by biochemical
experiments including a reporter assay combined with a pulse-chase assay. Our results showed that the Ago1-associated-complexes can react dynamically to
environmental condition and miRNA plays an important role for stress responses.
811A
Sensitivity to nicotine: Can a Regulated Mechanim's microRNAs?
Ivan Sanchez Diaz, Veronica Narvaez Padilla, René Hernandez Vargas, Enrique
Reynaud Garza. Genetica del Desarrollo y Fisiologia Molecular, Instituto de Biotecnologia, Cuernavaca, Cuernavaca, Mexico.
It has been amply demonstrated that of all the compounds in tobacco, nicotine is the molecule responsible for causing addiction. The study of the
susceptibility to nicotine and drugs in general, is very complex because addiction depends on both genetic and environmental factors. Drosophila
melanogaster has been used to study addiction. Using volatilized nicotine, we isolate a line (L-70) that showed increased sensitivity to nicotine in relation wt.
The line L-70 has a P-element (p {GawB}) in the region of the genome designated as 2R:16470008 which corresponds to an intergenic region, near a cluster
of micro-RNA 's (mir-310/311/312/313) which become over express by the presence of this insertion in the adult stage. We also show that removing the P-
element in this region is restored wild phenotype and levels of micro-RNA's become wt. Interestingly knockout flies of this cluster (Δ 40) show a resistance
phenotype compared to control. Based on these data we hypothesized regulation of the response to nicotine in the fly through these mir's. This regulation
would be mediated through the inactivation of target the mirs genes.
812B
mir-11
limits the pro-apoptotic function of its host gene,
dE2f1
.
Mary Truscott
1
, Abul Islam
2
, Núria López-Bigas
2
, Maxim Frolov
1
. 1) Department of
Biochemistry & Molecular Genetics, University of Illinois at Chicago, Chicago, IL; 2) Department of Experimental and Health Sciences, Barcelona
Biomedical Research Park, Univ Pompeu Fabra, Barcelona, Spain.
The E2F family of transcription factors regulates the expression of both genes associated with cell proliferation, and genes that regulate cell death. The net
outcome is dependent on cellular context, and tissue environment. The mir-11 gene is located in the last intron of the Drosophila E2F1 homolog gene, dE2f1,
and its expression parallels that of dE2f1. We investigated the role of miR-11, and found that miR-11 specifically modulated the pro-apoptotic function of its
host gene dE2f1. A mir-11 mutant was highly sensitive to dE2F1-dependent, DNA damage-induced apoptosis. Consistently, co-expression of miR-11 in
transgenic animals suppressed dE2F1-induced apoptosis in multiple tissues, while exerting no effect on dE2F1-driven cell proliferation. Importantly, miR-11
repressed the expression of the pro-apoptotic genes rpr and hid, which are directly regulated by dE2F1 upon DNA damage. In addition to rpr and hid, we
identified a novel set of cell death genes that were also directly regulated by dE2F1 and miR-11. While some of these genes displayed increased enrichment
for dE2F1 following irradiation, some did not, suggesting a different context for their regulation. Thus, our data support a model in which the coexpression
of miR-11 limits the pro-apoptotic function of its host gene, dE2f1, upon DNA damage by directly modulating a dE2F1-dependent apoptotic transcriptional
program. Furthermore, dE2F1 and miR-11 may intersect in the regulation of cell death genes in contexts beyond irradiation-induced apoptosis.
813C
Genetic analysis of a pseudogene and its parent gene in Drosophila melanogaster.
G. Elizabeth Sperry, Denise V. Clark. University of New Brunswick,