Smiley-8: Retroviruses and Hepadnaviruses

Question 1

Are retroviruses enveloped?

Answer 1

yes

Question 2

Describe genome of retrovirus

Answer 2

ssRNA, +ve sense

Question 3

How is the retrovirus genome capped and polyadenylated?

Answer 3

coded for by the genome (done by RdRNAP)

Question 4

Provirus

Answer 4

• dsDNA transcript from +ve sense ssRNA

- integrates to host chromosomes

Question 5

Where are progeny virions assembled in the host cell?

Answer 5

plasma membrane

Question 6

How do retroviruses acquire their envelope?

Answer 6

by budding out of host cell

Question 7

What is inside the retrovirus capsid? (x3)

Answer 7

• 2 identical copies of RNA genome
• RTase
• integrase

Question 8

Function of integrase

Answer 8

integrate linear dsDNA into host chromosome

Question 9

What cells do most retroviruses infect effectively?

Answer 9

actively dividing cells

Question 10

What does an LTR contain?

Answer 10

• RNAPII promoter

- polyadenylation signal

Question 11

Function of LTR

Answer 11

Directs production of RNA transcripts of integrated provirus using host machinery

Question 12

What does gag encode?

Answer 12

polyprotein to make viral capsid proteins

Question 13

What does pol encode?

Answer 13

RTase, RNAse H, and integrase

Question 14

What does env encode?

Answer 14

envelope proteins

Question 15

What does pro encode?

Answer 15

protease to cleave polyprotein to make capsid proteins

Question 16

HIV: What does tat do?

Answer 16

• transcriptional activator

- increase transcription driven from viral LTR

Question 17

HIV mRNAs are divided into 3:

Answer 17

• unspliced
• singly spliced
• multiply spliced

Question 18

What do unspliced and multiply spliced HIV mRNAs encode?

Answer 18

structural proteins and viral enzymes packaged into virions

Question 19

What do multiply spliced mRNAs code?

Answer 19

non-structural regulatory proteins: tat, rev, nef

Question 20

During early infection of HIV, only ____ mRNAs are made (what type of splicing)?

Answer 20

multiply spliced

Question 21

Function of rev (x3)

Answer 21

• helps drive infection to late phase to make unspliced and singly spliced transcripts
• suppress further splicing of transcripts to which it is bound
• promotes export from nucleus to cytoplasm

Question 22

Does RTase have proof-reading ability?

Answer 22

no