Virology Final Exam - Rui Lu

Which HBV protein contains the virus attachment site?

The L protein

Describe how HBV enters host cell

endocytosis

HBV virion, a P protein is often covalently linked to which strand of viral genomic DNA

minus stranded genomic DNA

describe how the protein of HBV is translated

leaky scanning

does hbv genome replication require a primer? if yes whats the nature and identity of the primer

yes, primer is the protein domain of the P protein

which hbv proteins can not be found in non infectious HBV particles

C and P proteins

does formation of covalently closed circular DNA (cccDNA) of HBV occur in cytoplasm?

no, in nucleus

describe how HBV genes are expressed.

- transcription template?

which host enzyme performs transcription to produce viral mRNAs?

- do all viral mRNA have the same 3' ends?

- how many types of proteins are produced by HBV?

- host RNA polymerase II transcribes viral mRNA using the covalently closed circular dsDNA molecule

- 4 types of mRNAs produced

- yeah each 3' end is polyadenylated using the same polyadenylation signal (TATAAA)

- seven main proteins: core, pre-core, small s, middle s, large s, polymerase, and HBx

describe structure of influenze

- enveloped

- segmented genome

- minus stranded

- has matrix protein

- viral genome packaged by nuclear protein in helical symmetry

which enzyme replicates the genome of influenza viruses?

rna dependent rna polymerase

which proteins form the genome of influenza virus?

PA, PB1 and PB2

Can Tamiflu/oseltamivir be used to treat influenza virus infection?

yes it inhibits the function of N protein and neuraminidase

how does influenza virus enter host cell?

endocytosis

where does influenza A virus replicate their genomic RNAs within host?

nucleus

transcription of influenza A virus mRNAS needs primers, where do the primers come from?

host primary mRNAs

describe the difference between antigenic drift and antigenic shift

-antigenic drift: gradual accumulation of genetic mutations in viral genome

- antigenic shift: genome reassortment

is lysogeny a type of non productive infection?

yes

describe the structure feature and genome constitution of phage X174, phage T7 Phi6 and phage MS2

- Phage 174 is a ssDNA which a icosahedral five fold axis and has 11 proteins

- Phage T7 Phi6 has a segmented dsRNA genome packaged in a polyhedral inner core with a lipid containing envelope. it's genome comprised of 3 linear segments: RNA L large, RNA M medium, and RNA S small

- Phage MS2 is a small icosahedral virus with ssRNA surrounded by 180 coat protein subunits

describe the genome constitution of phage lambda

dsDNA genome with cohesive ends which allows for the genome to circularize for enhanced stability

studies on replication of which class of viruses led to the discovery of rolling circle replication mode?

ssDNA phages

gene expression in ssRNA phages is often regulated by secondary structure of the viral genome, give evidence

varying ribosome binding sits (RBSs) are available at different times during translation

- only coat protein gene RBS is accessible initially

- replicase RBS only available after coat protein has been translated

(coat protein can repress the replicase gene if never translated)

phage T4 was suggested to be used as therapeutic agent for the treatment of diarrhea caused by some E. coli strains why?

T4 is a virulent phage which always causes lytic infection

filamentous ssDNA phages have been extensively used as cloning vectors, why?

-relatively small size and non-lytic infection cycle suggest easy manipulation and straightforward usage as cloning vectors

- filament size governed by size of genomic DNA, insert DNA can be very big

- vectors are based on the RF, easily obtained from infected cells. cloned ssDNA can be recovered from the phage particles for direct use in DNA sequencing, designing DNA probes and site directed mutagenesis

what kinds of genes are defined as proto-oncogene

proto-oncogenes are cellular genes that promote the normal growth and division of cells. they can cause cancer when overexpressed

what are tumor repressor genes?

suppress of inhibit the conversion of normal cell into cancer cell. these genes cause cancer when turned off

T or F

"oncogenic virus usually refers to those viruses that can replicate in cancer cells"

False, oncogenic viruses are those viruses that are able to cause cancer

describe basic biological properties such as capsid symmetry and genome constitution of human papillomavirus

naked virus with icosahedral capsid

- circular dsDNA

some oncogenic viruses can produce proteins that are able to inhibit function of P53 (tumor suppressor). give 4 examples

1. SV40 large T (tumor) antigen (binds to p53 and Rb)

2. KSHV latency associated nuclear antigen (binds to p53 and Rb)

3. HTLV-1 Tax protein binds to p53

4. HBV X protein binds to 53

describe the4 theories that explain why viral infection can lead to development of cancer

1. interference with control of the cell cycle (like a hijacking) - virus produced proteins inhibit the function/stability of important cellular proteins involved in cell cycle control

2. accidental activation of cell genes - enhance the expression of host proto-oncogenes

3. oncogenes carried by virus - some retroviral genomes carry oncogenes derived from cell proto-oncogenes which can become oncogenes when mutated or aberrantly expressed

4. damage to the immune defense - breakdown of immune defenses that may allow the development of cancer

do inactivated virus vaccines trigger both T and B cell mediated immune response?

no, they trigger B cesl mediated immune response

is it appropriate to inoculate immunocompromised people with live attenuated virus vaccine?

no, live virus can cause disease in immunocompromised people

T or F

"Rapid eradication of smallpox disease can be attributed to the fact that smallpox virus infection often produces clear disease symptom"

True

high incidence clear disease symptom helps us to monitor virus spread, which is important for us to eradicate the virus

virion subunit vaccine?

subset of viral proteins

what the definition of IC50 and SI during antiviral drug study?

an ideal antiviral drug should have what kind of IC50 and SI values?

IC50 is the percent inhibitory concentration and SI is selectivity index

IC50: low

SI: high