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13 Cards in this Set

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  • Back
What two types of disease do retroviruses cause?
1. T-cell proliferative dz (Tcell leukemia)

2. T cell death (HIV causes AIDS)
Compare exogenous and endogenous transmission of retroviruses:
Exogenous (horizontal) - HIV, transmitted between animals

Endogenous (vertical) - transmitted in the germ line. 5% of our human genome is made of endogenously transmitted genes!

What does the interior core of the retrovirus contain?
1. two identical (+)RNA
2. gag proteins (packaged with RNA)
3. Enzyme: reverse transcriptase (RT), ribonuclease H (RNaseH), integrase (int), and protease (pro).
What are retrovirus capsomeres?
They are a bunch of gag proteins that surround the core to make the nucleocapsid.

Describe the retroviruses nucleocapsid:
It is an envelop, one containing gags and host cell plasma membranes acquire during budding (inside the membrane there are env gene products which are glycoproteins that mediate both viruses binding to uninfected host cells and uncoating of envelop)

Describe the appearance of retrovirus RNA:

What is the order of the genes?
retrovirus RNA is capped and polyadenylated (resembling mRNA)

The order of the genes is always 5' gag-pol-env 3'

Does the + RNA of retroviruses serve as mRNA aftern infection?
Retrovirion RNA is reversed transcribed by the virion RT soon after infection --> proviral DNA (ds DNA)

Describe the proviral DNA of retroviruses:
1. double stranded, cDNA
2. longer than genomic RNA
3. ends have identical sequencyes called long terminal repeats (LTR)--- gag-pol-env DNA is flanked by LTR's and integrated into the host chromosomal DNA!!

What information is contained within the LTR's of retroviral proviral DNA?
LTR's have sequences for:
1. to promote integratin of provirus
2. promote transcription of integrated proviral DNA into mRNA

What component of retroviruses determines what cell it binds to (ex. CD 4+ for HIV virus)?
Env protein (example = gp120 is an env protein, it binds to CD4)

Where are retrovirus' reverse transcribed?
In cytoplasm!

What must happen before the virus can be fully duplicated?
After reverse transcription the dsDNA must be transported into the nucleus and INTEGRATED into the genome (integrase recognizes LTR's)

In a productive infection, once the retrovirus is integrated into the genome, what happens?
5' LTR promotes transcription of GAG-POL-ENV genes. And NEEDS transcription factors from host cell to make the two copies of viral mRNA's needed!