mock qualifying exam
TRANSCRIPT
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Identification of a daf-3 corepressor and mechanism of cofactor switch in high temperature induced dauer
formation
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L1
L2
L3
Dauer
L4
Egg
Adult
C. Elegans Life Cycle
Adverse ConditionsFavorable Conditions
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Lack of Food
Dauer Inducing Factors
HeatOvercrowding
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TGF-B in Dauer Formation
daf-5
daf-1 daf-4
daf-3
Dauer promoting genes
daf-7
daf-14daf-8
Pheromone
TGF-β Pathway <26°C
daf-3
TGF-β Pathway >26°C
Dauer CONSTITUTIVEDauer DEFECTIVE
daf-5
No Effect
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HYPOTHESIS
daf-5
daf-1 daf-4
daf-3
Dauer promoting genes
daf-7
daf-14daf-8
Pheromone
TGF-β Pathway >26°C
coREP
daf-3
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Specific Aims
Identify daf-3 corepressor in high temperature induced dauer formation
Determine the mechanism of daf-3 cofactor exchange.
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Specific Aim 1: Identify the daf-3 corepressor
RNAi mediated loss of known daf-3 binding proteins in WT
Non-lethal deletion mutants loss of known daf-3 bindg proteins
DAF-C PHENOTYPE AT 27°C
VSAdult Dauer
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Specific Aim 1: Identify the daf-3 corepressor
Protein extract from 20C and 27°CALTERNATE APPROACHES
Purified with daf-3 antibody20°C 27°C
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Specific Aim 1: Identify the daf-3 corepressorALTERNATE APPROACHES
Two Dimensional Gel
Identification of proteins by MALDI-MS
pH
Size
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daf-5daf-3
Dauer promoting genes
coREP
• Temperature dependent cofactor expression
Real-time PCR of daf-5 and the corepressor at 20°C and 27°C
20°C 27°C
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daf-5daf-3
Dauer promoting genes
coREP
• Temperature dependent cofactor expression
Ectopically express daf-5 and the daf-3 corepressor with HSP-GFP transgenics
20°C (+) Pheromone27°C (-) Pheromone
•Expect dauer promoting conditions•Expression of the corepressor should result in REDUCED dauer formation •Expect dauer repressing conditions•Expression of daf-5 should result in INCREASED dauer formation
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daf-5daf-3
Dauer promoting genes
coREP
Competitive binding of the corepressor
•Corepressor-RFP/daf-5-CFP/daf-3-GFP young adults at 20°C and 27°C
RFP CFPGFP
20°C27°C
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daf-5daf-3
Dauer promoting genes
coREP
Changes in daf-3 structures
20°C 27°CRNA Isolation
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20°C 27°C
Changes in daf-3 structures: Northern Blot
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Isoform XDaf-3 Null
+
Changes in daf-3 structures: Isoform Rescue
27°C
SUPPRESSION OF THE DAF-C PHENOTYPE
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Specific Aims 2:Determine the mechanism of daf-3 cofactor exchange.
• Temperature dependent cofactor expression - real-time PCR of daf-5 and the corepressor at 20°C and 27°C
- Ectopically express daf-5 and the daf-3 the corepressor with HSP-GFP transgenics
• Competitive binding of the corepressor- corepressor-RFP/daf-5-CFP/daf-3-GFP young adults at 20°C and 27°C
• Changes in daf-3 structures- Examine relative amounts of daf-3 mRNA isoforms a-c at
both 20°C and 27°C via northern blot
- Rescue the daf-d phenotype at 27°C by expression of isoform’s cDNA in the daf-3 mgD90 mutant