[barota]

sorry but you guys were wrong

HBV carries its own DNA-dependent DNA polymerase. it's different from reverse transcriptase, AKA RNA-dependent DNA polymerase

becacuse HBV virus is partially double stranded circular DNA... that means partially single strand part of DNA must be elongated to be complete circular double stranded DNA...

In this process, they use their own DNA-dependent DNA polymerase. They carry that enzyme inside the virus, and not make it inside the human cell. This is the reason why purified HBV virion itself is not infectious.. they need DNA-dependent DNA polymerase, which is already carried by the virus.

After completing making a double strand DNA, they use cellular(human's) RNA polymerase to make mRNA from complete dsDNA.

They also make reverse transcriptase from this mRNA. and use RT to make viral dsDNA from mRNA they made.

newly made dsDNA is enclosed in the envelope and exit the cell

To sum up...

DNA-dependent DNA polymerase: carried as enzyme itself by HBV virus to elongate its incomplete dsDNA to make complete dsDNA after entry to the human cell.

Reverse transcriptase: carried as gene inside the HBV gemone, translated from HBV mRNA which is made from HBV genome by human's RNA polymerase.

 

[barota]

continue..

to help understanding.....

partial dsDNA -------> complete dsDNA ------> mRNA --------> dsDNA
1 2 3

1. by DNA-dep DNA polymerase(HBV's) : HBV carries this enzyme.. so the purified genome of HBV itself would not be infectious (they need this enzyme in the viral particle)

2. by DNA-dep RNA polymerase(host's) : host enzyme is needed, located in the nucleus.

3. by reverse transcriptase(= RNA-dep DNA polymerase) : translated from HBV's mRNA which is made from HBV genome by host's RNA polymerase(#2)

 

[barota]

thanks

@barota
You are mostly right and have explained it well.

Just want to add,
The HBV DNA polymerase is a dual-function enzyme that carries out not only DNA-dependent DNA replication(to synthesize missing portion of DNA) but also RNA-dependent DNA replication (reverse transcriptase) activity.
So it is the same enzyme!

References:
http://www.medscape.com/viewarticle/440517_2
and
Review of medical microbiology and immunology By Warren Levinson. Page 294
http://books.google.com/books?id=Q_...itis b virus dependent DNA polymerase&f=false

@MSC
Hi~
thanks for your comment.
Good luck