Where does reverse transcriptase come from?

[thestrokes14]

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When a retrovirus, such as HIV, infects a eukaryotic cell, for example, where does the enzyme "reverse transcriptase" come from so that the RNA can be converted to cDNA?

 

[LaurenMCAT]

When a retrovirus, such as HIV, infects a eukaryotic cell, for example, where does the enzyme "reverse transcriptase" come from so that the RNA can be converted to cDNA?

Hi thestrokes

I'm of the understanding that the retrovirus brings the reverse transcriptase enzyme with 'em. It's certainly not part of the eukaryotic cell normally!

 

[thestrokes14]

Hi thestrokes

I'm of the understanding that the retrovirus brings the reverse transcriptase enzyme with 'em. It's certainly not part of the eukaryotic cell normally!

Thanks. I know that answer seems obvious, but I was under the impression that the virus was only injecting the DNA or RNA contained within the capsid of the virion. I guess, can a retrovirus also inject enzymes into the host cell?

 

[MilkIsGood]

Thanks. I know that answer seems obvious, but I was under the impression that the virus was only injecting the DNA or RNA contained within the capsid of the virion. I guess, can a retrovirus also inject enzymes into the host cell?

yes. reverse transcriptase is present in the virus

 

[donkeykong1]

yup, its one of the few things that the virus [albeit retro] itself contributes when taking over a host.

 

[Zedor]

The enzyme is coded for by a nucleotide sequence within the viral RNA.

 

[LaurenMCAT]

Thanks. I know that answer seems obvious, but I was under the impression that the virus was only injecting the DNA or RNA contained within the capsid of the virion. I guess, can a retrovirus also inject enzymes into the host cell?

No worries! To double check, I went back on Wikipedia and there was no other explanation given.

 

[Zedor]

No worries! To double check, I went back on Wikipedia and there was no other explanation given.

http://en.wikipedia.org/wiki/Pol_(HIV))

 

[Pamplemousse123]

I had a question similar to this too:
In EK Bio, pg 57 on the microbio section: the question asks:
49. which of the following events does not play a role in teh life cycle of a typical retrovirus?
a. viral dna is injected into the host cell
b....
c. the gene for RTase is transcribed and the mrna is translated inside the host cell.
d. ....

answer is a fyi
just wanted to confirm this: RTase is being made inside the host cell not to RT the virus' RNA but rather to pack it with other viral components so that the cell can expel the virus in the lytic cycle?

 

[thestrokes14]

I had a question similar to this too:
In EK Bio, pg 57 on the microbio section: the question asks:
49. which of the following events does not play a role in teh life cycle of a typical retrovirus?
a. viral dna is injected into the host cell
b....
c. the gene for RTase is transcribed and the mrna is translated inside the host cell.
d. ....

answer is a fyi
just wanted to confirm this: RTase is being made inside the host cell not to RT the virus' RNA but rather to pack it with other viral components so that the cell can expel the virus in the lytic cycle?

The answer is A because retroviruses inject RNA into their host. It appears that this RNA codes for reverse transcriptase, and the host cell ribosomes/tRNA/amino acids probably translate this sequence to produce the enzyme itself. Then reverse transcriptase produces cDNA from the originally injected RNA, which then enters the lysogenic stage? by incorporating into host cell nuclear DNA. Then as the cell replicates, the viral DNA replicates, and will eventually reenter the lytic stage and lyse the cell.

Can someone confirm that this is not bogus? 🙂

 

[jissho]

When a retrovirus, such as HIV, infects a eukaryotic cell, for example, where does the enzyme "reverse transcriptase" come from so that the RNA can be converted to cDNA?

Humans have a reverse transcriptase called telomerase. It can only use a special RNA template to add "TTAGGG" DNA repeats to the ends of chromosomes.

 

[TXKnight]

When a retrovirus, such as HIV, infects a eukaryotic cell, for example, where does the enzyme "reverse transcriptase" come from so that the RNA can be converted to cDNA?

reverse transcriptase is encoded by retrovisuses

 

[ModernAlchemist]

To OP: It's prepackaged in the capsid usually, so reverse transcription can be done immediately upon infection of a target cell. This is typical of a single-stranded + RNA virus.

To thestrokes: Injection doesn't actually occur in HIV infection. It's actually a form of endocytosis that involves HIV binding to specific receptor glycoproteins on the surface of your cells. When you refer to injection, it's usually wish bacteriophages that have that mechanism. So, ya the entire virus is taken into the target cell and then the capsid is broken down while the virus replicates. Also, the way I learned it in virology was that bacteriophages have a lysogenic phase, but the phase is called latency for eukaryotic cell viruses. During latency, the genome of the virus is incorporated into the cell's genome as a provirus using the protein integrase encoded for on the retroviral genome. Like you said, the cell then replicates the viral genome along with its own genome. It's pretty crazy how stealth the HIV virus is. This way it can still survive even if its original RNA genome is destroyed by cellular defenses.

 

[thestrokes14]

To OP: It's prepackaged in the capsid usually, so reverse transcription can be done immediately upon infection of a target cell. This is typical of a single-stranded + RNA virus.

To thestrokes: Injection doesn't actually occur in HIV infection. It's actually a form of endocytosis that involves HIV binding to specific receptor glycoproteins on the surface of your cells. When you refer to injection, it's usually wish bacteriophages that have that mechanism. So, ya the entire virus is taken into the target cell and then the capsid is broken down while the virus replicates. Also, the way I learned it in virology was that bacteriophages have a lysogenic phase, but the phase is called latency for eukaryotic cell viruses. During latency, the genome of the virus is incorporated into the cell's genome as a provirus using the protein integrase encoded for on the retroviral genome. Like you said, the cell then replicates the viral genome along with its own genome. It's pretty crazy how stealth the HIV virus is. This way it can still survive even if its original RNA genome is destroyed by cellular defenses.

Thanks for the clarification!

 

[vickpick]

RTase is a part of retroviruses. For the virus that goes into a lysogenic phase, RNA is RTed to cDNA and incorporate into host enzyme. For a virus that goes into the lyric cycle, the RNA is translated to create more copies of RTase to package in newly formed viruses.