RETRO Flashcards
What enzyme does this virus family use to produce DNA intermediates from their RNA genome?
Reverse Transcriptase
An RNA-dependant DNA polymerase that is present within the virions of all members of the family.
Reverse Transcriptase
True or False
Retro viruses infect a wide variety of animals and humans , can produce latent infections, and are associated with certain types of cancers.
TRUE
Retro
ENVELOPED or NOT?
ENVELOPED
Name the 3 genes that all non defective retroviruses have.
GAG- encodes virion core proteins
POL- encodes reverse transcriptase and integrase
ENV- encodes the envelope proteins
How does the virus penetrate the cell membrane?
Membrane Fusion
Can the virus use endocytosis or exocytosis to gain entry inside the cell?
Endocytosis
Unlike HIV, Retros do not need a co factor.
True or False
False
Retro viruses may require a co receptor like HIV
What enzyme is used to intergrate the viral DNA into the host cellular chromosomal DNA ?
Integrase enzyme
Maturation of virions occurs by _________ through the host cell plasma membrane.
BUDDING
Assembly and packaging of viral protein, encapsidation or viral RNA occurs in the ___________.
Cytoplasm
_____________ is replicated with host genome and can be passed to daughter cells resulting in transmission from one generation to the next.
PROVIRUS
The replication of retros is accompanied by high mutation frequency that is due to the lack of _________________ by reverse transcriptase.
3’ to 5’ exonuclease proofreading mechanism
What are non pathogenic DNA stretches found widely in genome of most vertebraes that closely resemble retros?
Endogenous retroviruses
All RNA tumor viruses belong to the family Retroviridae.
TRUE or FALSE
TRUE TRUE TRUE
What gene does the acute transforming retroviruses carry that makes them directly oncogenic by having the power of unregulated expression and are under the control of viral LTRs?
v-onc
Remember: c onc/proto oncogenes are host genes that encode important cell signaling porducts that regulate normal cell proliferation
What gene does the virus loose during recombination and what gene does the virus aquire?
Looses its own ENV gene
Gains the host PROTO-ONCOGENE
Note: This makes v-onc containing viruses unable to synthesize a complete envelope, are replication defective and must associate with non defective viruses to replicate
**EXCEPTION: Rous sarcoma virus **
A type of Retrovirus that does not contain the v-onc gene.
Slow/Chronic Transforming Retrovirus
Etiology
Bovine Leukemia
(Enzootic Bovine Leukosis)
Deltaretrovirus
What is the unique sequence in Bovine Leukemia Virus that is not of host cell origin between ENV and 3’LTR?
pX
What is the regulatory protein that is encoded in the pX region, activates the replication of BLV and contributes to the induction of lymphoma(oncogenesis)?
Tax protein