Micro: CH 9 Viral replication strategies

What are the 4 steps of viral replication?

Recognition of host cells

Viral entry and uncoating

Viral replication

Viral assembly and egress

What does host range mean?

Viruses can only infect a specific range or type of cells.

How is host range determined?

By the interactions between viral attachment proteins and host cell receptors

Entry type for enveloped virus INFLUENZA

Endocytosis

Entry type for Enveloped virus HIV

Membrane fusion

Entry type for nonenveloped virus

Receptor mediated endocytosis

Entry type for bacteriophages

Direct insertion of genome

Entry type of plant viruses

Through damaged regions of the cell because it can’t go through the cell wall

Where do typical eukaryal viruses replicate?

In the host cell nucleus

Where do atypical eukaryal viruses replicate?

In the host cell cytoplasm

T/F: Negative sense RNA (-RNA) can be translated by the host cell

FALSE! It must be converted into +RNA to be translated by the host cell.

What do -RNA viruses use to convert to +RNA genome?

Viral RNA dependent RNA polymerase (RdRp) makes a complementary +RNA

What type of virus uses reverse transcriptase to convert their ssRNA genome into dsDNA genome?

Reoviruses or retroviruses

What do typical eukaryal viruses use from the host cell in replication?

Host cells DNA polymerase, RNA polymerase, and ribosomes

What do atypical eukaryal viruses use from the host cell in replication?

Host cells ribosomes

It brings its own RNA polymerase, and transcription factors

What is the Temperate phase of bacteriophage replication?

Virus integrates its genome with host cell genome and then just chills until the host cell divides to replicate its genome.

What happens in the lytic cycle of bacteriphage replication?

The virus immediately replicates in the host cell then lysis it and released new viruses.

What is a lambda phage?

a bacteriophage that can undergo temperate phase or lytic phase depending on the ratio of 2 repressor proteins

What are the 2 repressor proteins that determine if a lambda phage uses the lytic phase or lysogenic phase?

Cl repressor and Cro protein

What cycle does the Cl repressor promote the lambda phage to do?

It promotes the lysogenic cycle

What cycle does the Cro protein promote the lambda phage to do?

It promotes the lytic cycle

What is function 1 of repressor protiens?

Bind to specific DNA sequences like promoter regions

What is function 2 of repressor proteins?

Prevent RNA polymerase from attaching to a promoter region

What is function 3 of repressor proteins?

Prevent transcription of genes into mRNA

What is function 4 of repressor protiens?

mRNA gets bound by an RNA binding repressor and stops mRNA from being translated into a protein

What does assembly mean?

Putting together new viruses

Many virus parts can self assemble using no extra energy which makes the process fast and cheap for the virus

What does egress mean?

Exit the cell

What does the mechanism of egression depend on?

The virus type and the host cell

How do enveloped viruses egress?

By embedding viral proteins into the host plasma membrane then docking to them and budding out of the cell, typically taking a part of the host cells PM with them

How do non enveloped viruses egress?

Almost always by lysis of the host cell

How do plant viruses egress?

Many move from cell to cell by cytoplasmic connections

Move from one plant to another by disruption of the cell wall