(12) Retroviridae

Question 1

(Retroviral Gene organization)

Pick from HTLV, HIV, WDSV, ALV, HFV, and MLV

1. Which of these are simple?
2. Which are complex?
3. What is the difference?

Answer 1

1. ALV and MLV
2. HTLV, HIV, HFV, and WDSV
3. Complex contains accessory genes that code for for additional regulatory non-virion proteins derived from multiply spliced messages

(noticegag-pol-env sequence in both)

Question 2

1. What are remnanats of ancient retroviral infections of the host germline transmitted vertically from generation to generation?
2. How have they persisted?
3. Infectious? capable of replication?
4. They co-evolve with host species
5. Some ERVS are used by the host as restriction factors to block the infection of what?

Answer 2

1. endogenous retroviruses (ERVs)
2. in the genome of their hosts for thousands of years
3. for a short time after integration; no (all appear to be defective)
4. pathogenic retroviruses

Question 3

(characteristics of retroelements in eukaryotic genomes)

1. Up to what percentrage of animal genomes contain retroelements? How are these elements distinguished from retroviruses?
2. What gene do they lack that makes them noninfectious?

Answer 3

1. 10% (42% of human); lack of an extracellular phase
2. env gene

Question 4

(Retroviruses)

1. Enveloped or no?
2. genetic form?
3. What is the life cycle?
4. What is nucleic acid in virus? in infected cell?
5. Simple vs. complex exogenous
6. endogenous retroviruses vs. retroelements (?)

Answer 4

1. enveloped
2. single-stranded (+) RNA viruses with a diploid genome

(This large and diverse family includes members that are oncogenic, are associated with a variety of immune system disorders, and can cause degenerative and neurological systems)

3. RNA-DNA-RNA
4. RNA, DNA

Question 5

(Retroviral life cycle)

just look at slide

Answer 5

if you want to watch a movie about it

Question 6

(Envelope Proteins)

1. Which protein is involved in receptor recognition?
2. What triggers the fusion of the viral and cellular membranes?

Answer 6

1. surface glycoprotein (SU)
2. transmembrane glycoprotein (TM)

(some examples)

Question 7

1. What is responsible for making a DNA copy of the RNA viral genome?
2. Drugs?

Answer 7

1. reverse transciptase
2. Major class of anti-HIV drugs are RT inhibitors

Question 8

(Integration of Provirus)

1. Provirus complexed with protein moves to nucleus - what is this called?
2. Most retroviruses require cells going into mitosis for he breakdown of what?
3. HIV and related viruses can enter intact nuclei, so no need for what?

Answer 8

1. pro-integration complex
2. the nuclear membrane (so productive infection only in dividing cells)
3. cell division (can actively infect non-dividing cells)

Question 9

(Integration of Provirus)

1. Integrase performs what two function?
2. Does this lead to immediate expression of viral genes or little to no expression (laten)?

(When this cell divides so does the genomes and get daughter cells with viral genome)

3. reversible of irreversible?
4. Can result in insertional mutagenesis that can lead to what?

Answer 9

1. cuts up DNA of cell and seals provirus in the gap
2. can be either
3. irreversible (advantage as gene therapy vectors)
4. oncogenesis

Question 10

(After budding, Virus Goes from Immature to Mature Form)

1. Mature form (after budding)
2. What happens?
3. Do all retroviruses have same morphology in mature form?

Answer 10

2. Core becomes more dense
3. no - they can have different morphology

Question 11

(Protease)

1. how many units?

just read this

Answer 11

1. dimer

Question 12

(Summary - Part II)

1. enveloped or no?
2. Lipid bilayer that contains what?
3. Have outer matrix protein and inner core capsid containing what?
4. Genome?
5. All retroviruses contain what 3 genes? simple retrovirus (MLV)? complex retrovirus (HIV)?
6. What is used to generate DNA?
7. Viral genome is integrated into host genome - called what?
8. Progeny Virus produced using host cell transcriptional and translational machinery. Are retroviruses like other viruses obligate intracellular parasites?

Answer 12

1. enveloped
2. viral spike glycoproteins
3. viral genome
4. two copies of single stranded positive-stranded RNA (8-10 kb)
5. gag, pol, and env; only these 3; additional genes involved in replication and pathogenesis
6. reverse transcriptase
7. provirus
8. yes

Question 13

1. Some retroviral genomes contain what that cause cancer?

Answer 13

1. oncogenes

Question 14

(Some mechanisms of how retroviruses can cause Cancers)

1-4. by expressing viral oncogenes, which transform infected cells. the viral oncogenes mimic what 4 things?

5. Also do this by activating what?
6. By inactivating what?

Answer 14

1. growth factors
2. growth factor receptors
3. intracellular signal transducers
4. nuclear transcription factors
5. cellular oncogenes (cis-activating retrovirus)
6. nearby cellular tumor repressor genes

Question 15

(Some mechanisms of how retroviruses can cause cancers)

Question 16

(Transmission)

1-2. Can be transmitted from one animal to another by what 2 distinct modes?

3. vertical transmission can be as what or what?

Answer 16

1. horizontal
2. vertical
3. as virions or in the germ plasm (provirus)