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Poster Full Abstracts - Regulation of Gene Expression
Poster board number is above title. The first author is the presenter
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histone 3 lysine 9 (H3K9) methylation at the promoter. Using ChIP analysis we find that ASH1 protein associates with
Sxl
Pe
sequences, placing it at the
promoter during
Sxl
Pe
expression. Our data suggest that these proteins modify the epigenetic environment at
Sxl
Pe
to ensure proper regulation of the sex
determination process in males and females.
760A
Retinal determination factor Eyeless and type I bHLH protein Daughterless directly induce onset of
atonal
expression and synergistically induce
retinal development.
Miho Tanaka-Matakatsu, Wei Du. Ben May Dept Cancer Res, Univ Chicago, Chicago, IL.
Induction of the proneural gene
atonal
(
ato
) expression is a key step for the retinal progenitor cells to initiate photoreceptor neuron differentiation. Retinal
determination factor Eyeless (Ey) has been shown to directly activates the
ato
early eye enhancer,
ato-3'
, through a conserved Ey binding site. The initiation
of photoreceptor differentiation and
ato-3'
expression are negatively regulated by EMC, which functions by binding to the type I bHLH transcription factor
Daughterless (Da). We show that Ey and high level of Da overlap near the Morphogenetic Furrow (MF) region and that
da
mutant clones spanning the MF
exhibit delayed onset of the
ato-3’
enhancer activation while Da over-expressing clones near the MF show precocious activation. Furthermore, expression of
Da and Ey in wing tissues synergistically activates the
ato-3’
enhancer and increases the ectopic eye sizes, suggesting that Ey and Da synergistically
activates the
ato-3'
enhancer and controls proper timing of photoreceptor cell differentiation during eye development. To dissect the mechanisms involved in
the synergistic activation, we found that the Ey site in
ato-3'
enhancer overlaps with an E box binding site. Mutations that disrupt either the Ey binding site
or the E box binding site impairs the activity of
ato-3’
enhancer, indicating both Ey and Da-Da are required for the full
ato-3'
enhancer activity. Furthermore,
the observed interactions between Ey and Da are conserved in mammalian systems and that observed effect of Da is likely mediated by Da-Da homodimer
since linked Da homodimer but not linked Da heterodimer is functional. We will present a model by which the retinal determination factors and the bHLH
family of proteins coordinate to control the onset of photoreceptor differentiation.
761B
Transcriptional and Metabolic Adaptation to Hypoxia is Driven by HIF-Independent Actions.
Keith D. Baker
1
, Yan Li
1
, Divya Padmanabha
1
, Luciana
B. Gentile
1
, Catherine I. Dumur
2
. 1) Biochemistry and Molecular Biology, VCU School of Medicine, Richmond, VA; 2) Pathology, VCU School of
Medicine, Richmond, VA.
Hypoxia-inducible factors (HIFs) are the vanguard of the transcriptional response to hypoxic conditions, where they direct oxygen-sensitive changes that
allow for homeostatic adaptation. While it is assumed that HIF-mediated actions shift metabolic strategy to allow for adaptation, the contribution that HIFs
provide has not been well examined. Here, we examine hypoxic responses in wild-type and
dHIF
mutant animals using transcriptional and metabolic
profiling and provide integrated views of the transcripts and metabolites that change in response to hypoxia in
Drosophila
. Unexpectedly, we find dHIF has
a greater impact on metabolism in normoxia than in hypoxia, and that a majority of hypoxia-induced metabolic changes still occurs in
dHIF
mutants.
Consistent with the dissociative nature of HIF from hypoxia-induced shifts, we show that dHIF-independent actions are responsible for inducing glycolytic
transcripts. Our analysis also reveals distinct roles of dHIF-dependent and -independent activity on various aspects of adaptive metabolism. These data
suggest that low oxygen conditions trigger different response pathways, with the driver of metabolic adaptation being dHIF-independent responses.
762C
The
Drosophila melanogaster
gene
tfiia-s-2
encodes a male germline-expressed homolog of the small subunit of the TFIIA general transcription
factor.
Amory Brandt, Cameron Jernigan, Margaret Wood, Cynthia Cain, Mark Hiller. Biological Sciences, Goucher College, Baltimore, MD.
Eukaryotic general transcription factors are protein complexes that help position RNA polymerase at promoters and initiate transcription. The general
transcription factors TFIIA and TFIID assemble on promoters early in the process of transcription initiation. TFIIA consists of three protein subunits. In
D.
melanogaster
, a single gene,
tfiia-l
, encodes a 48 kD polypeptide that is proteolytically cleaved to form two proteins of 30 kD and 20 kD.
tfiia-s
encodes the
small subunit of 14kD. We have shown that a homolog of the small subunit,
tfiia-s-2
(CG11639), is expressed only in the male germline. We have also
shown that two transcripts are encoded by
tfiia-s-2
, and that both proteins are able to interact with the generally expressed large subunit when expressed in
E.
coli
. Together, this suggests that three different forms of TFIIA might be present in the male germline. TFIID is comprised of TATA-binding protein (TBP)
and up to fourteen TBP-associated factors (TAFs). Several testis-specific TAFs have been identified, and mutations in the testis-TAFs cause defects in
transcription and block spermatid differentiation. It is possible that complexes containing testis-TAFs and testis-specific TFIIA-S-2 function together to
regulate gene expression in the testis. We are examining this possibility by making a mutation in the
tfiia-s-2
gene by homologous recombination in order to
examine the phenotype of a
tfiia-s-2
mutation. We are also characterizing the ability of complexes containing TFIIA-S-2 to physically associate with TFIID
subunits and testis-expressed homologs of TFIID subunits.
763A
The investigation of a novel Y chromosome specific gene in
Anopheles stephensi
.
Frank Criscione, Yumin Qi, Zhijian Tu. Department of Biochemistry,
Virginia Tech, Blacksburg, VA.
Anopheles
mosquitoes are the main malaria vectors and their sexual determination is controlled by a dominant male-determining factor on the Y-
chromosome. However, the properties of this Y-chromosome factor responsible for the initiation of the sexual determination cascade have yet to be
elucidated, but would provide strong support to genetic strategies of vector population control. We use
Anopheles stephensi
, one of the main mosquito
vectors of the malaria parasite in India and the Middle East, as a model to study Y-specific genes that may be involved in sex determination. Using next-gen
sequencing and a comparative bioinformatic approach, we identified a small number of Y-chromosome gene candidates and confirm localization to the Y
chromosome. This study focuses on male-specific gene 1(MSG1) that is transcribed at the very onset of the maternal-zygotic transition and expressed solely
in the early embryo. Using RT-PCR, we confirmed the expression pattern of this gene. We hypothesize that MSG1 is the male-determining factor. Biological
function of MSG1 is being tested through the use of both transient and transgenic siRNA and ectopic expression of MSG1.
764B
The transcription factor network patterning Drosophila photoreceptors.
Hui-Yi Hsiao, Robert Johnston, Dave Jukam, Claude Desplan. Dept Biol, New