Section 6.1

Question 1

Animal Virus Genome:

Answer 1

DNA (mostly ds)

Question 2

The larger the DNA genome, the greater _________ from Cellular Machinery

Answer 2

Independence

Question 3

Cytoplasmic-replicating DNA viruses encode their own:

Answer 3

DNA polymerase AND RNA polymerase

Question 4

Nuclear-replicating DNA viruses encode their own:

Answer 4

DNA polymerase
but use host cell’s RNApol

Question 5

1) Herpersviridae: frequently show _____-_______ ________ and is never cleared from the body

Answer 5

life-long persistence

Question 6

a herpesviridae viruses infect ___

Answer 6

nervous system (neurotropic)

Question 7

B and Y herpesviridae viruses infect ___

Answer 7

lymphatic system (lymphotropic)

Question 8

Examples of herpesviridae:

Answer 8

EBV (Epstein-Barr virus), HSV-1, HSV-2, Chicken pox (varicella zoster virus VZV)

Question 9

facts about EBV

Answer 9

• originally discovered un human tumor cells
• 95% of adults carry it from early life infection
• initial infection can be either asymptomatic or cause mononucleosis
• replicates in mucosal cells “kissing disease” and becomes latent in B cells

Question 10

Structure of herpesviridae:

Answer 10

• icosohedral nuclear capsid (made of 6 proteins)
• wrapped in envelope
• envelope covered with 10< glycoproteins
• matrix (tegument) : large space between envelope and capsid made up of 15-20 proteins

Question 11

matrix (tegument) is a :

Answer 11

large space between envelope and capsid made up of 15-20 proteins

Question 12

Function of matrix: (2 things)

Answer 12

1) structural support (maintains structure of virion)
2) released after infection in host cell to do stuff

Question 13

What do Herpesviruses first do?

Answer 13

1) initiate a primary productive infection by
- replicating its DNA
- forming viral particles
- killing host cell
- release progeny viruses
initial symptoms of oral sores, genital sores or chicken pox

Question 14

After Herpesviruses productive infection:

Answer 14

• immune response limits viral replication
• viral DNA enters LATENT state

then two options:
1) remain without symptoms, no infectious virus is detectable in latent phase
2) reactivation of latent virus can lead to another productive infection

Question 15

Herpes Simple Virus (HSV) genome:

Answer 15

• linear dsDNA —–> circulaires in latency
• 3 repeated sequences and 2 unique regions

-ends have packaging signals (from concatamer made in replication)

Question 16

Steps of entry of HSV:

Answer 16

• HSV glycoproteins: attachment and fusion with cell membrane
• capsid and matrix proteins: release into cytoplasm

-nucleocapsid: goes to nucleus of cell with the help of host microtubule cytoskeleton

• capsid: docks at nuclear pore complex

—–> viral DNA released into nucleus and capsid remains in cytoplasm

Question 17

HSV gene expression stages (3 gene classes)

Answer 17

1- immediate early genes (5 genes)
2- early genes
3- late genes

Question 18

HSV gene expression STAGE 1 immediate early genes

Answer 18

transcription
VF16 (aka aTIF) needs to go into the nucleus for transcription to occur

Question 19

HSV gene expression STAGE 2
Early genes:

Answer 19

Activated by the products of the IE genes

• encode DNA replication functions

Question 20

HSV gene expression STAGE 3
Late genes:

Answer 20

structure and egress expression starts after DNA replication has begun

Question 21

HSV replicates its DNA using: ___ _____ _______ method

Answer 21

RCR: rolling circle replication

Question 22

How does RCR work

Answer 22

• it generates a continus strand of concatameric viral DNA
• this concatameric DNA is the substrate for encapsidation
• cleavage encapsidation protons recognize the a sequences (later becomes the ends) and puts everything else in between

Question 23

Final packaged DNA by RCR is called a ________

Answer 23

procapsid

Question 24

HSV replicates in ______ ________

Answer 24

replication factories

Question 25

in HSV replication factory:

Answer 25

Viral DNA replicates

late genes get expressed

> 30 genes assemble the vision

Question 26

mature HSV capsid leaves nucleus through _____ ______

therefore undergoing:

Answer 26

double nuclear membrane

1- primary envelopment: to acquire mature envelop structure

2- secondary envelopment: in a secretory vesicle that then fuses with plasma membrane to release virion from cell

Question 27

herpesviruses get their envelopes from ________ ___ _______

Answer 27

Inside the cell
NOT BY BUDDING OUT THE CM

Question 28

productive infection of HSV-1 happens in __ __________ where new visions are produced

Answer 28

lip epidermis (hence cold sores)

Question 29

HSV-1 latent infection

Answer 29

HSV-1 is neurotropic: enters a sensory neuron at infection site

capsid migrates within neuron and enters nucleus but cannot be productive
——-> cuz no cellular protiens in neuron’s for IE genes

Question 30

During latent infection period of HSV-1

Answer 30

DNA present as histone wrapped mini chromosome
—-> transcription is therefore repressed and no DNA can replicate

Only reactivated by stress or other stimulus, leading to infectious visions reproduced and going to epidermal lip tissue