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Virology > HBV > Flashcards

HBV Flashcards

1
Q

What family is HBV in?

What genus is HBV in?

A

Family - hepadnaviridae

Genus - Orthohepadnavirus

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2
Q

Which 3 HBV particles are there?

A

22nm HBsAg
45nm Dane Particle
Pleiomorphic HBsAg filaments

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3
Q

Describe the HBV genome

A
  • relaxed circular DNA (rcDNA)

3. 2kb partially double stranded.

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4
Q

How is the circularity maintained?

A

Overlapping 5’ ends

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5
Q

Which strand in HBV is longer? The positive or negative strand?

A

Negative strand

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6
Q

What is required for attachment and entry of HBV?

A

L surface antigen.

Unknown receptor.

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7
Q

How is HBV taken up?

A

Endocytosis, membrane fusion occurs between viral and cellular membrane.

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8
Q

How does rcDNA convert to cccDNA?

A

P protein is removed

Both strands are completed and ligated by host cellular enzymes in the nucleus

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9
Q

What is the template for transcription for HBV?

A

cccDNA

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10
Q

What is the role of HBV X protein?

A

Transcriptional activator

Doesnt bind DNA itself, activates transcription factors and interacts with cell signalling papthways

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11
Q

What does nuclear export of mRNAs into the cytoplasm depend on?

A

Post transcriptional regulatory element - PRE. that uses the Crm1/RAN-GTP pathway but no viral protein is required.

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12
Q

There are 4 different mRNAs made in transcription in HBV. How long is each one and what does it encode?

A
  1. 5kb - pregenomic RNA, C and P protein
  2. 4kb - L form of the S antigen
  3. 1kb - M and S form of the S antigen
  4. 7kb - encodes X protein
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13
Q

How is the 3.5kb mRNA translated?

A

Leaky scanning.

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14
Q

How is the 2.1kb mRNA translated?

A

It has 2 promoters very close together. The 1st encodes the M antigen and the 2nd initates txn just downstream of the start site.

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15
Q

What is the signal for core particle assembly in HBV?

A

P:RNA complex

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16
Q

Compare the HIV and HBV reverse transcriptases

A

Both have polymerase and RNase H domain
HBV p protein has a spacer and terminal protein (larger N term domain)
Tyrosine 96 is the primer for -sense DNA strand synthesis whereas the HIV RT uses tRNA as a primer.

17
Q

What determined the fate of core particles in HBV?

A

Concentration of L surface antigen.

18
Q

What does low concentration of L lead to?

A

Core particle enters the nucleus and is converted to cccDNA

19
Q

What does a high concentration of L lead to?

A

Core particle buds into the ER. Virions exit the cell by exocytosis.

20
Q

What happens to empty HBsAg particles?

A

Bud into the ER and undergo exocytosis.

Virology (6 decks)

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