Lec 14: Hepadnaviruses (Hep B Virus) Flashcards
Hepadnaviruses: Cause _______ and they have ___ genomes
hepatitis
DNA
Hepadnaviruses Unique characteristics: (2)
- ) have very small genomes, which are used with great economy to encode the virus proteins and to control expression of the virus genes.
- ) their DNA genomes are replicated via an RNA intermediate.
Hepadnaviruses class? =
Class VII
____ ______ people may have been infected with HBV.
~400 million
Over 50 million new HBV infections each year, mostly in
babies who acquire the infection from their mothers.
Many HBV infections result in…
However, the infection in children is…
…mild symptoms or are asymptomatic, especially in children
…most likely to become persistent, 90-95% vs 1-10% in adults.
Individuals who are persistently infected with HBV may…
…remain healthy for much of the time, but some develop severe hepatitis, which may eventually lead to liver cancer
Hepadnaviruses are present in
the blood and semen of infected individuals.
Hepadnaviruses mode of transmission is
similar to that of HIV.
HBV Virion shape =
roughly spherical, with a diameter of 42 nm.
HBV Virion also has
envelope enclosing a capsid, with DNA and P (polymerase) protein inside.
HBV Genome =
Also…
two strands of DNA
…one of which is incomplete; hence the DNA is partly single stranded and partly double-stranded
(HBV Genome)
A short sequence is…
…triple-stranded as a result of a complementary sequence at the 5 ends, and this results in the DNA having a circular conformation.
(HBV Virion)
At the 5’ end of each of the DNA strands there is
…a covalently linked molecule:
- a capped RNA on the short strand and
- a protein (P) on the long strand.
P (polymerase) protein =
a multifunctional protein!
P (polymerase) protein activities: (3)
- ) reverse transcriptase activity
- ) ribonuclease H (RNase H) activity (catalyzes the cleavage of RNA)
- ) DNA-dependent DNA polymerase activity