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6 retroviruses Flashcards

1
Q

retrovirus viron structure?

is there an envelope?

what is the genomic material like?

A

it is enveloped

and the matirix is under a lipid bilayer.

there are 2 copies of the + ssRNA

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2
Q

retrovirus

what is differenet about its gemonoic material?

A

it has 2 copies of + ssRNA

it is the only virus that is diploid.

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3
Q

C) Simple retrovirus genomic organization!

what is R for?

what is the U5 for?

A

R is for repeat because it is onboth ends.

U5 is for unique to the 5’end.

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4
Q

C) Simple retrovirus genomic organization!

what is the gag gene?

A

encodes the gag proteins MAtrix, CApsid, NucleoCapsid, and

PRotease. The proteins are made as a polyprotein that then gets clipped (see

below) - NOTE: in some viruses, like HIV, PR is in the pol gene reading frame!

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5
Q

Simple retrovirus genomic organization!

what is the pol gene for?

A

the polymerase (pol) gene: encodes reverse transcriptase (RT) and integrase

(IN), which are made as an extended polyprotein (see below)!

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6
Q

retorvirus genomic organization

what is the env gene for?

A

encodes the env protein, which is made as a precursor

and gets cleaved into the surface (SU) and transmembrane (TM) domains (in

HIV, gp160 -> gp120 and gp41, see below)!

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7
Q

retrovirus genomic organization?

what is the U3 for?

A

it is unique to the 3’ end.

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8
Q

HIV has complex retrovirus organization what does this mean?

A

Organized similar to simple retroviruses (w/ gag / pol / env), except numerous additional genes / proteins.!

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9
Q

The first phase (steps A-E) precedes integration

what are those steps?

A

A- Adsorption !!
B- Penetration and uncoating!
C- Reverse Transcription!
D- Transit to the nucleus!
E- Integration into host DNA!

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10
Q

the second phase (F-J) is post- integration.!

A

F- Viral RNA synthesis, host pol II! G- RNA processing!
H- Virion protein synthesis!
I- Assembly and budding!
J- Capsid maturation (proteolysis)

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11
Q

Adsorption: step?

what happens?

A

virus binds to cell via the env protein.

hiv uses cd4/CCr5

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12
Q

B. Penetration* and uncoating

what happens?

A

Viral envelope fuses with cell

membrane either i) at the cell!
surface or ii) in endosomes after endocytosis: *two antivirals to this step*, as will be discussed later!

THE GENOMIC RNA is only partially uncoated.

it remains in a protein particle in the cytoplasm

YOU DONT WANT TRANSLATION AT THIS POINT BECAUSE YOU ARE IN THE CYTOSOL AND YOU HAVE SSRNA

YOU WANT TO MAKE dsDNA and integrate it in to the cells genome.

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13
Q

what converts ssRNA to dsDNA?

A

reverse transcriptase

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14
Q

what is the integrated DNA called?

what is the long terminal repeats called?

A

the provirus it is longer than the template RNA b/c it has U3 and U5 repeated at the ends.

LTR are U3 and U5 repeated at the ends.

so it is U3 R U5

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15
Q

where does the reverse transcriptase act?

A

it does its work in the cytoplasm.

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16
Q

what are the polymerase activites of the reverse trascriptase?

A

– an RNA-dependent DNA polymerase (copies RNA to DNA)!

– a DNA-dependent DNA polymerase (copies a 2nd strand of DNA from the first strand)!

– is an ‘error prone’ polymerase, ~5 errors per made per genome, which accounts

for rapid evolution and drug resistance!

!

17
Q

what protein carries out the integration of the cell with the virus?

what sequence does integrace recognize?

can most retroviruses cross the nuclear membrane?

A

integrase (IN)

it recognizes the end sequences U3 and U5

no most cannot. HIV can though.

18
Q

what drug atacks Reverse transcriptase?

A

AZT

19
Q

what drug attacks integrase?

A

Raltegravir

integrase is the only protein that causes the virus to get included in the host genome. that is why it is a good target.

20
Q

what is the major role of the LTR?

where is the binding site?

where does the transcription begin?

A

to direct synthesis of viral RNA.

the 5’ U3 has the binding sites for the cellular transcription factors.

R is where the transcription begins.

21
Q

what are the 2 fates of the full length RNA?

what happens to the RNA that is spliced?

A

they can become genomic RNA

or gag-pol RNA

spliced RNA can go on to make env RNA

22
Q

how is just gag made?

how is gag-pol made?

what on happens more often?

A

gag has a AUG start and a stop codon at the end of gag

starts at the gag AUG start and ignores the gag stop.

more often there is a just gag is made and only 5% of the time is gag-pol made.

23
Q

what breaks up the gag-pol polyprotein?

A

PR

only outside of the cell once it has budded off.

Both the gag and gag-pol proteins are eventually cleaved by the protease (PR) domain, releasing the individual proteins!

24
Q

what needs to happen to the env protein?

A

it is made from spliced mRNA

in ER bound ribosomes

has to go thorugh the ER and golgi to be insereted in to the plasma membrane.

25
Q

what needs to happen to the env protein for it to be infectios?

A

it has it be cleaved form the gp160 to gp120-140 otherwise it can not support membrane fusion

IT WONT BE INFECTIOUS WITHOUT THE CLEVAGE.

26
Q

retrovirus

what signal is needed for packaging?

where is this signal included in?

A

the psi signal

it is in the unspliced but not the spliced RNA

splicing removes it.

27
Q

how does buddin ghappen?

A

the gag and gag-pol polyproteins recruit RNA

gag interacts with the envelope and budding occurs.

28
Q

how does maturation of retro virus happen?

where does it happen?

what protein does it?

A

it happens in outside of the host cell

after budding has occured

it is done by the PR protein causeing the rearrangement of the gag pol polyprotein.

blocking maturation is the basis of the HIV PR inhibitors.

29
Q

what are non transforming retroviruses?

how long do they take to make tumors.

do they have oncogenes?

how do they cause tumors?

A

they are non acute or slow tumor viruses

the tumors take 6 months to a year to appear.

they do not transform cells in culture.

they dont have oncogenes

the tumors are caused by the inactivation or activation of the host genes.

30
Q

what are transforming retroviruses?

how long does it take to make tumors?

what do they do to tissue cultures?

do they have oncogenes in them?

A

they cause tumors within weeks

they case tissue culture cells to become transformed or be cancer like

they hve oncogenes “a mutated copy of a cellular gene involved in growth control”

infection fo the virus introduces the oncogene and causes rapid tumor onset.

31
Q

why are most oncogene containg viruses defective?

A

they are defective b/c teh oncogene replaces one or more of the viral genes.

32
Q
A

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