Steps 5-7: Assembly and Exit (Lecture 15)

Question 1

What are the 3 common de novo reactions necessary for viral reproduction?

Answer 1

forming structural unit, assemble capsid, incorporate genome

Question 2

What are the 3 things that viral proteins need to interact with?

Answer 2

with each other, genome, lipid membrane (envelope viruses)

Question 3

What are 4 host cell processes that viruses rely on and why?

Answer 3

chaperones (protein folding), transport systems, secretory pathways, and nuclear import/export

Question 4

What is short distance viral movement dependent on?

Answer 4

protein channels

Question 5

Where are protein channels found on?

Answer 5

plasma membrane, nuclear membrane, golgi

Question 6

What is long distance movement dependent on?

Answer 6

cytoskeleton tracks such as motor proteins and microtubules

Question 7

What kind of cytopathic effects do viruses cause that lead to inclusion bodies? What are inclusion bodies?

Answer 7

conentration of proteins on internal membranes due to viral factories; inclusion bodies are fragmented organelles

Question 8

What are inclusion bodies called in rabies viruses?

Answer 8

Negri bodies

Question 9

What does it mean when it says that viral proteins have zip codes?

Answer 9

viral proteins contain signal sequences

Question 10

What role do the signal sequences have on the viral proteins?

Answer 10

helps them get to the targeted area where they need to go

Question 11

What are the 4 types of zip codes?

Answer 11

membrane targeting, membrane retention, nuclear localization and retention signals

Question 12

What are membrane targeting signals?

Answer 12

also can be fatty acid modifications that target these proteins to the membrane

Question 13

What are membrane retention signals?

Answer 13

signals that retain the proteins on the membrane so that they don’t get secreted or go anywhere else

Question 14

What are nuclear localization and export signals?

Answer 14

directs proteins that need to get in or out of the nucleus

Question 15

What type of pathway does localization of viral proteins to plasma membrane?

Answer 15

secretory pathway

Question 16

What are 3 ways that viruses assemble their protein coats?

Answer 16

assembly from individual protein molecules that will come together, from a polyprotein precursor that will fold on its own or get cleaved, or use chaperones

Question 17

How does the virus distinguish which genome to package from the cellular DNA/RNA molecules during encapsidation?

Answer 17

based on packaging signals embedded on viral genome

Question 18

What types of packaging signals do DNA viruses have?

Answer 18

located near inverted repeats and origin, it is complex

Question 19

What types of packaging signals do RNA viruses have?

Answer 19

are often secondary structures and is varied

Question 20

What is the mechanism of release for envelope virions?

Answer 20

assemble at and bud from plasma membrane OR via exocytosis

Question 21

What is the mechanisms of release for non-enveloped virions?

Answer 21

induce cellular death pathway = causes membrane to rupture/bleb so virus can get out || lyse cell by puncturing holes on cell membrane via viral proteins || inhibit cellular pathways that can compromise structural integrity so the cell will fall apart and virus can get out

Question 22

What are the 4 ways that viruses can obtain an envelope?

Answer 22

viral glycoproteins integrated into membrane interact with nucleocapsid proteins || use internal matrix proteins or capsid proteins to drive budding || membrane proteins themselves can drive budding || matrix proteins mainly drive budding but need additional components to increase budding efficiency

Question 23

Where are membrane proteins synthesized?

Answer 23

rough endoplasmic reticulum