Several virus-coded enzyme activities are generally required for the replication of viral DNA. These are helicase (with ATPase activity) to unwind the double helix, helix-destabilizing protein to keep the two separated strands apart, DNA polymerase to copy each strand from the origin of replication, RNAse to degrade the RNA primer after it has served its purpose, DNA ligase to join the Okazaki fragments together

1. Replication of DNA viruses
Dr Vikramaditya Upmanyu
Division of Biological Standardization

2. Parvo,circo
Cellular DNA pol
dsDNA
Adeno, herpes Pox, Asfa
mRNA
Cell RNA
polymerase II
Cell RNA polymerase II
Virion transcriptase
Virion DNA
polymerase
Virion DNA
polymerase
Polyoma, Paplioma
cellular DNA
polymerase

3. Several virus-coded enzyme activities are generally required
for the replication of viral DNA
 Helicase (with ATPase activity) to unwind the double
helix
 helix-destabilizing protein to keep the two separated
strands apart
 DNA polymerase to copy each strand from the origin of
replication
 RNAse to degrade the RNA primer after it has served its
purpose
 DNA ligase to join the Okazaki fragments together
Replication of Viral DNA

4. Paplioma and polyomavirus
Genomic
dsDNA
Replicated dsDNA
in the nucleus
1
Early gene
products;
oncoproteins
Cell cycle
induction;
S Phage entry
Transcription of
early gene
products;
translation
Virus assembly
Progeny virus
Late gene product;
Structural gene
Transcription of
late gene
products;
translation
Genomic replication by cellular
DNA poly
Entry and transport of DNA to
nucleus
6
5
4
3
2
Transformation
Papovavirus genome, with its associated
cellular histones, morphologically and
functionally resembles cellular DNA and utilizes
host cell enzymes, including DNA polymerase A
for its replication.
An early viral protein, large-T, binds to sites in the
regulatory sequence of the viral genome, thereby
initiating DNA replication. Replication of this circular
double-stranded DNA commences from a unique
palindromic sequence and proceeds simultaneously
in both directions

5. Adenovirus
Genomic dsDNA
Replicated dsDNA
in the nucleus
1
Early gene
products;
oncoproteins
Cell cycle
induction;
S Phage
entry;
Apoptosis
inhibition
Transcription of
early gene
products by
DdRpII; translation
Virus
assembly
Progeny virus
Late gene product;
Structural gene
Transcription of
late gene
products
byDdRpII;
translation
Genomic replication by cellular
DNA poly
Entry and transport of DNA to
nucleus
7
6
5
4
2
Transformation
VA RNAs;
IFN antagonist
Transcription of
VA gene
products by
DdRp III;
translation
3

6.  Adenovirus DNA is linear, with the 5' end of each strand
being a mirror image of the other (terminally repeated
inverted sequences)
 Each is linked covalently to a protein, the precursor of
which serves as the primer for viral DNA synthesis.
 DNA replication proceeds from both ends, continuously
but asynchronously in a 5' --~ 3' direction, using a virus-
coded DNA polymerase.
 It does not require the synthesis of Okazaki fragments
Adenovirus DNA

7. Herpes viruses
Genomic dsDNA
Replicated dsDNA
1
α gene products; β
gene TFs
Virus assembly
Genomic replication by Viral
DNA poly
Nucleus transport & circularization of DNA
4
β gene products; γ
gene TFs
γ gene products; Most
structural protein, α TIF
3
5
6
2
γ gene expression
β gene expression
α gene expression
Progeny virus
Encode many or all of the proteins
required for DNA replication, including
a DNA polymerase, a helicase, a
primase, a single-stranded DNA
binding protein, and a protein
recognizing the origin of replication

8. Parvovirus
Genomic DNA
Replicated
dsDNA
concatamer
1
Nonstructural protein
Virus assembly
Entry & transport of ssDNA to nucleus
2
Structural protein
6
3
Concatamer
resolution
Transcription by DdRpII;
translation
Progeny virus
Genomic-length
dsDNA hairpin
4
5
Progeny ssDNA
genome
Transcription by DdRpII;
translation
2nd Strand DNA synthesis
during S Phage
Full DNA replication by cellu
DNA Polymerase
3'-palindromic sequences that form a
double stranded hairpin structure as a
primer for cellular DNA polymerase
binding

9. Pox virus
Core containing ds dsDNA
Replicating dsDNA
in the cytoplasm
1
Early gene products;
DNA polymerase,
Intermediate TFs
Virus assembly &
morphogenesis
DNA release; genomic
replication by Viral
DNA poly
Viral core enter in the
cytoplasm
3
Intermediate gene
products; Late TFs
Late gene products;
Most structural proteins,
Early TFs
4
5
7
2
Late gene
expression
Early gene expression by
Viral transcriptase,
Translation
Progeny virus
Replicated dsDNA
in the cytoplasm
6
Intermediate gene
expression
Genomic replication
by Viral DNA poly
self-sufficient in DNA replication machinery.

10. THANK YOU