VIRUSES ENCODE INFORMATION FOR

1
VIRUSES ENCODE INFORMATION FOR

• ENSURING GENOME REPLICATION
• ENSURING GENOME PACKAGING
• ALTERATION OF STRUCTURE AND/OR FUNCTION OF THE
  HOST CELL

2
STRATEGY

• WAY IN WHICH VIRUS CARRIES OUT THESE FUNCTIONS
• look out for weak points

3
INTRACELLULAR PARASITES
Nucleus (SV40)

• NEED TO OBEY RULES
• OR BE ABLE TO BEND THE RULES

cytoplasm (a paramyxovirus)
Hsiung and Fong, from Hsiungs Diagnostic
Virology 1994
4
DNA VIRUSES

• mRNAs needed to make proteins
• host has a DNA-dependent RNA polymerase, plus the
  additional proteins need to make properly
  modified mRNA
• need to replicate their DNA
• host has a DNA polymerase, plus the additional
  proteins needed to replicate DNA
• THIS MACHINERY IS IN THE NUCLEUS

5
CYTOPLASMIC DNA VIRUSES

• need to code for cytoplasmic DNA and RNA
  polymerases
• need to code for accessory proteins needed for
  DNA and RNA synthesis
• will have large genomes
• poxvirus family (30-75 times genome size of the
  smallest nuclear DNA viruses parvoviruses and
  polyomaviruses)

6
DNA genome sizes ( bases)

• Parvoviruses 5 kb
• Polyoma 5 kb
• Papilloma 8 kb
• Adenoviruses 30-42 kb
• Herpesviruses 120-200 kb
• Poxviruses 130-375 kb
• E.coli 4700 kb

7
PARVOVIRUSES

• SMALL DNA VIRUSES
• parvo small (18-25nm)
• SINGLE STRAND DNA
• 5 kilobases (5000 nucleotides)
• REPLICATE DNA IN NUCLEUS
• Human B19 parvovirus infects dividing cells
  (primarily erythroid progenitors)
• ICOSAHEDRAL SYMMETRY

8
PAPILLOMAVIRUSESPOLYOMAVIRUSES

• small (40-60nm)
• icosahedral capsid
• mainly VP1
• some VP2, VP3
• non enveloped
• ds DNA (circular)
• associated with histones
• genome
• Papilloma 8 kb (kilobases)
• Polyoma 5 kb

human papillomavirus Murray Fig. 49.1
9
PAPILLOMA VIRUSES
WARTS SOME PAPILLOMA VIRUSES ARE ASSOCIATED
WITH CANCER
human papillomavirus Murray Fig. 49-4
10
POLYOMAVIRUSES
PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY (PML)
TUMORS IN ANIMALS
http//medstat.med.utah.edu/WebPath/TUTORIAL/AIDS/
AIDS.html10
11
POLYOMAVIRUS FAMILY

• POLYOMA VIRUS
• SV40 VIRUS
• BK VIRUS
• JC VIRUS
• LYTIC CYCLE
• NON-LYTIC CYCLE

12
ADSORPTION, PENETRATIONUNCOATING
OUTSIDE
ds DNA histones
NUCLEUS
CYTOPLASM
17
13
LYTIC CYCLE

• EARLY PHASE - GENERAL
• PROTEINS NEEDED FOR DNA REPLICATION
• REGULATORY PROTEINS
• OFTEN PROTEINS WHICH ALTER HOST CELL
• LATE PHASE - GENERAL
• DNA REPLICATION
• NEW STRUCTURAL PROTEINS

14
EARLY mRNA SYNTHESIS
0
20
80
DNA
60
40
SV40 (polyoma virus)
modified from Fiers et al., Nature 273113
15
HOST DNA REPLICATION MACHINERY HOST CELL HISTONES
DNA SYNTHESIS
SV40 (polyoma) virus
16
HOST CELL HISTONES
0
20
80
DNA
60
40
17
0
20
80
DNA
60
40
LATE mRNA SYNTHESIS
SV40 (polyoma virus)
modified from Fiers et al., Nature 273113
18
NH2 - met - ala - pro - thr - lys - ..... VP1
G A U G G C C C C A A C A A A A
. . . . . . .
asp - gly - pro - asn - lys - ...... VP2, VP3
19
ROLES OF LARGE T ANTIGEN

• DNA replication

20
ROLES OF LARGE T ANTIGEN

• DNA replication
• increased transcription of late genes

21
ROLES OF LARGE T ANTIGEN

• DNA replication
• increased transcription of late genes

22
ROLES OF LARGE T ANTIGEN
A

• DNA replication
• increased transcription of late genes
• decreased transcription of early genes

A
23
ROLES OF LARGE T ANTIGEN

• DNA replication
• increased transcription of late genes
• decreased transcription of early genes

A
24
ROLES OF LARGE T ANTIGEN

• DNA replication
• increased transcription of late genes
• decreased transcription of early genes
• cellular transformation

25
ASSEMBLY

• NUCLEUS
• CAPSID PROTEINS
• HISTONES
• inclusion bodies

26
RELEASE

• CELL LYSIS

27
SOME FEATURES TO NOTE

• early and late functions
• multiple use of the same DNA sequence
• multifunctional protein
• small genome - few proteins
• host cell provides
• DNA synthesis machinery
• RNA synthesis machinery
• histones

modified from Fiers et al., Nature 273113
28
ADENOVIRUSES

• linear, double stranded DNA (30-42 kb)
• non-enveloped
• icosahedral
• 70nm diameter

http//www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/em_adeno
.gif
29
ADENOVIRUSES

• upper respiratory tract infections
• conjunctivitis
• gastrointestinal infections
• cystitis
• tumors in some animals

30
ADENOVIRUS VIRION
A

• more proteins
• more hexons
• linear DNA
• no histones

http//www.embl-heidelberg.de/ExternalInfo/fuller/
ad2fb.gif
Fields et al., Fundamental Virology, 1996
31
ADSORPTION, PENETRATION, UNCOATING
Zinsser Microbiology 20th Ed.
32
EARLY mRNA SYNTHESIS
Adapted from Broker,T.R. In Processing of RNA.
(Apirion, D ed) 181-212, 1984
33
Early proteins include proteins which
Adapted from Broker,T.R. In Processing of RNA.
(Apirion, D ed) 181-212, 1984

• are needed for transcription of other early mRNAs
• E1a gene product
• are needed for DNA synthesis
• alter expression of host genes
• may interfere with the host anti-viral defenses
• interfere with cell cycle regulation

34
DNA REPLICATION
35
DNA REPLICATION
36
DNA REPLICATION
terminal protein (TP)
37
DNA REPLICATION
single strand binding protein
38
Adapted from Broker,T.R. In Processing of RNA.
(Apirion, D ed) 181-212, 1984
39
monocistronic mRNA problem
AAAAAAAA
mRNA
RIBOSOMES
PROTEIN
40
(No Transcript)
41
ASSEMBLY

• assemble in nucleus
• maturation stage
• release by cell lysis
• excess structural proteins

Koneman et al. Color Atlas and Textbook of
Diagnostic Microbiology 5th Ed. 1997
42
SOME FEATURES TO NOTE ABOUT ADENOVIRUSES

• larger and more complex than papovaviruses
• code for their own DNA polymerase and DNA
  packaging proteins
• early genes scattered, late genes in a block
• host cell provides
• DNA synthesis accessory factors
• RNA synthesis and modification enzymes
• so not surprising that go to nucleus

43
Adapted from Broker,T.R. In Processing of RNA.
(Apirion, D ed) 181-212, 1984
44
HERPESVIRUSES
icosahedral nucleocapsid
nucleocapsid from http//hub.med.uth.tmc.edu/hon
g/image.html
45
HERPESVIRUSES

• LARGE GENOME
• polyoma 5 kb
• adeno 30-42 kb
• herpes 120-220 kb

• herpes simplex virus
• Epstein Barr virus
• chicken pox/shingles (varicella zoster virus)

electron micrograph by Linda Stannard http//www.
uct.ac.za/depts/mmi/stannard/emimages.html
46
herpesviruses, paramyxoviruses, HIV
47
INFECTED CELL
UNINFECTED CELL
48
INFECTED CELL
UNINFECTED CELL
49
INFECTED CELL
UNINFECTED CELL
50
(No Transcript)
51
SJ Flint et al. Principles of Virology (2004)
HERPESVIRUS
HERPES SIMPLEX VIRUS
52
EARLY TRANSCRIPTION

• alpha-mRNAs (immediate early)
• virion protein (VP16) interacts with host
  transcription factor and increases the amount of
  transcription from the alpha promoters
• alpha proteins enable beta promoters to be
  recognized

SJ Flint et al. Principles of Virology (2004)
53
(DELAYED) EARLY TRANSCRIPTIONbeta-mRNAs

• beta-mRNAs code for
• DNA polymerase
• DNA binding proteins
• thymidine kinase
• ribonucleotide reductase
• etc
• beta protein synthesis results in decreased
  alpha-mRNA synthesis

54
DNA REPLICATION

• Virus codes for multiple proteins involved in
  replicating the DNA
• at least 6 viral proteins needed in addition to
  viral DNA polymerase
• DNA replication results in concatemers (long
  molecules containing multiple copies of the
  genome)
• DNA replication is accompanied by a lot of
  recombination
• may play necessary role

55
HERPES SIMPLEX GROUPpossible genome structures
unique long - UL
unique short - US
56
late (gamma-)gene transcription

• gamma-proteins are mainly structural
• probably one of the gamma proteins decreases beta
  expression
• a gamma-protein packaged in the virus is needed
  for alpha-gene transcription

SJ Flint et al. Principles of Virology (2004)C
57
gene organization

• no blocks for early or late genes

58
ASSEMBLY

• nucleus
• lot of virions, excess components
• nuclear inclusions
• buds through inner nuclear membrane
• de-enveloped at outer nuclear membrane
• re-enveloped in cytoplasm

T. C. Mettenleiter. Herpesvirus assembly and
egress. J.Virol. 76 (4)1537-1547, 2002.
59
CYTOMEGALOVIRUS IN LUNG OF AIDS PATIENT
http//medstat.med.utah.edu/WebPath/TUTORIAL/AIDS/
AIDS.html10
60
POINTS TO NOTE ABOUT HERPESVIRUSES

• NO OBVIOUS EARLY OR LATE GENE BLOCKS
• MORE INDEPENDENT THAN SOME OF THE SMALLER VIRUSES
• SINCE MORE INDEPENDENT - MORE WEAK LINKS FOR
  TARGETING WITH DRUGS

61
POXVIRUSES
lb - lateral body c - core
62
Human monkey pox - Wisconsin 2003
Medical College of Wisconsin/Froedtert
Hospital http//www.mcw.edu/derm/
63
ENTRY

• not clear if fusion with plasma membrane,
  endocytosis or both
• gets into cytoplasm, minus membrane

64
EARLY TRANSCRIPTION

• cytoplasmic

65
DNA
DNA
viral
RNA polymerase
66
EARLY TRANSCRIPTION

• cytoplasmic
• virally-coded RNA polymerase packaged in virion
• capping, methylation, polyadenylation enzymes in
  virion
• (naked DNA is not infectious)
• no spliced mRNAs known

67
IMMEDIATE EARLY GENE PRODUCTS

• play role in uncoating the virus further
• once uncoating proceeds, the other early genes
  are available for transcription

68
EARLY GENE PRODUCTS

• uncoating
• DNA replication
• RNA transcription and modification
• a few structural proteins are made

69
CYTOPLASMIC REPLICATION

• CYTOPLASMIC FACTORIES (Guarneri bodies)

CDC
Norrby et al., Medical Microbiology
70
DNA SYNTHESIS

• VIRALLY CODED MACHINERY

71
LATE TRANSCRIPTION AND TRANSLATION

• CONTROL VERY COMPLEX

72
ASSEMBLY AND MATURATION

• cytoplasmic
• slow
• wrapped by cellular membranes

F. A. Murphy, School of Veterinary Medicine,
University of California, Davis.
http//www.vetnet.ucdavis.edu/fam_graphics/downlo
ad.html
73
RELEASE
Baron et al., Medical Microbiology 1996
74
POINTS TO NOTE ABOUT POXVIRUSES

• CYTOPLASMIC
• LARGE GENOME
• DOES A LOT OF THINGS FOR ITSELF
• UNUSUAL CAPABILITIES