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S L I D E 1
Expression of Late Regulators in the Epstein-Barr Virus
Newlyn Joseph
El-Guindy Lab
August 21, 2014
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S L I D E 2
Epstein-Barr Virus (EBV/HHV-4)
• A very common virus in humans, responsible for infectious mononucleosis.
• It has also been associated with various forms of cancer including several lymphomas.
• Early infections are asymptomatic.
• Genome consists of about 85 genes.
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S L I D E 3
Latent State Lytic cycleReactivation
Very Early StageZEBRA & Rta (transcription activators)
Early StageViral Replication Proteins
DNA ReplicationZEBRA (Origin binding protein)
Late StageViral capsid proteins
Packaging& Egress
EBV-infected cell
Dependent on replication
BGLF3BGLF4“BGLF4 and BGLF3 are both
indispensable for late gene expression.”
EBV Life Cycle
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S L I D E 4
Why Study EBV?
• EBV’s only mode of propagation is via lytic replication.
– Studying the lytic cycle gives us insight into the general behavior of EBV.
• While much is known about ZEBRA and Rta (which play a role in lytic activation), the mechanisms that trigger late gene expression need to be further understood.
• There is a near universal presence of EBV in certain tumors.
– Oncolytic therapy is said to assist in the treatment of cancers.
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S L I D E 5
The BGLF3 Gene
• BGLF3 regulates late gene expression (viral structural proteins).
• BGLF3 encodes for a protein of an unknown function.
• The pEX system was used to express BGLF3 in E. Coli.
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S L I D E 6
The General Procedure
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S L I D E 7
After Expression
• Cells were lysed and the protein extract was suspended in binding buffer.
• The histidine tag present on the expressed protein allowed for nickel column affinity chromatography.
• SDS-PAGE was used to view the eluted protein purity.
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S L I D E 8
G3 Elution Results
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S L I D E 9
SDS-PAGE Nickel Column Purification Products
Increasing amount of Imidazole
150100
75
50
37
25
20
1510
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S L I D E 10
Final Steps
• The purified BGLF3 protein will then be cleaved of the Histidine and GST tags.
• An antibody will be generated from the protein.
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S L I D E 11
The BGLF4 Gene
• BGLF4, the only kinase encoded by EBV, phosphorylates various proteins, which in turn trigger late gene expression.
• Changing the 102nd amino acid (within the catalytic domain) from Lysine to Isoleucine yields an inactive kinase.
• This mutant is used to analyze the substrates and phosphorylating activity of BGLF4.
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S L I D E 12
Creating BGLF4(K102I)
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S L I D E 13
Expression of Mutant BGLF4
• After the mutation was confirmed via sequencing, analysis of the mutant kinase via Western Blot was used to verify inactivity.
• EBV Positive cells (without endogenous BGLF4) were exposed to the following:
– CMV (empty vector)
– ZEBRA
– ZEBRA + FLAG-BGLF4
– ZEBRA + FLAG-BGLF4(K102I)
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S L I D E 14
Hypothesis
• EA-D (an early protein) should not be hyper-phosphorylated.
– EA-D is a critical component of EBV DNA Polymerase.
• FR3 (a late protein) expression should be inhibited.
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S L I D E 15
Western Blot Results (I-125)
EA-D
FLAG
ZEBRA
FR3
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S L I D E 16
Conclusion
• BGLF4(K102I) is an inactive kinase.
• EA-D is hyper-phosphorylated by BGLF4.
• BGLF4 regulates the expression of the late protein FR3.
• FLAG-BGLF4(K102I) can be used in pull-down experiments to further study protein-protein interactions.
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S L I D E 17
Acknowledgements
• El-Guindy Lab
– Dr. Ayman El-Guindy
– Jessica McKenzie
– Kid’s Meeting• George Miller
• Discovery To Cure
– Dr. Gil Mor
– JoAnn Bilyard