Retroviruses
Summary
TLDRThis video explains retroviruses, a unique type of RNA virus characterized by the enzyme reverse transcriptase. The video details how retroviruses use reverse transcription to convert viral RNA into DNA, which integrates into the host cell's genome through another enzyme called integrase. Once integrated, the host cell unknowingly replicates viral RNA and proteins, creating new immature retroviruses. These new retroviruses then mature and are released to infect other cells, continuing the replication cycle. The video provides a step-by-step visual guide to this process.
Takeaways
- 🦠 Retroviruses are a type of RNA virus known for possessing the enzyme reverse transcriptase.
- 🔄 Reverse transcriptase allows the retrovirus to reverse the usual transcription process, turning viral RNA into viral DNA.
- 🧬 Retroviruses have additional enzymes like integrase, which integrate viral DNA into the host cell's DNA.
- 🧫 The retrovirus enters the host cell by fusing its lipid envelope with the host cell membrane.
- 💥 Once inside, the viral capsid breaks down, releasing viral RNA and enzymes into the host cell.
- 🔧 Reverse transcriptase binds to viral RNA, creating viral DNA, which is crucial for the virus’s replication process.
- ✂️ Integrase cuts open the host cell DNA and integrates the viral DNA into the host’s genome, forming a provirus.
- 📜 The host cell’s machinery then transcribes the viral DNA, producing multiple copies of viral RNA.
- 🛠 Ribosomes in the host cell translate viral RNA into viral proteins, including reverse transcriptase, integrase, and the viral capsid.
- 🚶♂️ The new viral proteins self-assemble into immature retroviruses, which are eventually released from the host cell to infect new cells.
Q & A
What is a retrovirus and what makes it unique?
-A retrovirus is a specific type of RNA virus that possesses an enzyme called reverse transcriptase. This enzyme allows the virus to perform reverse transcription, converting RNA into DNA, which is the reverse of the typical transcription process.
What role does reverse transcriptase play in the life cycle of a retrovirus?
-Reverse transcriptase binds to the viral RNA and performs reverse transcription, creating a DNA version of the viral RNA. This allows the retrovirus to integrate its genetic material into the host cell's DNA.
What is the function of integrase in a retrovirus?
-Integrase is an enzyme that helps integrate the viral DNA into the host cell's DNA by cutting open the host's DNA and inserting the viral DNA into it.
How does the retrovirus enter a host cell?
-The retrovirus attaches to the host cell membrane, and the lipid bilayers of both the virus and the cell fuse. This fusion allows the retrovirus to enter the host cell, where its capsid is dissolved to release the viral RNA and enzymes.
What is a pro-virus, and how is it formed?
-A pro-virus is a combination of the host cell's DNA and the viral DNA created after the viral DNA is integrated into the host genome. This integration is facilitated by the enzyme integrase.
How does the host cell’s transcription process contribute to viral replication?
-Once the viral DNA is integrated into the host DNA, the host cell's normal transcription machinery is used to create viral RNA. This viral RNA will then direct the production of viral proteins.
What happens to the viral RNA once it is created in the host cell?
-The viral RNA attaches to ribosomes in the host cell, where the ribosomes read the viral RNA and produce viral proteins, such as reverse transcriptase, integrase, and the viral capsid proteins.
How are new retroviruses formed inside the host cell?
-The viral proteins produced by the host cell’s ribosomes self-assemble into immature retroviruses. These immature viruses are then released through the host cell membrane.
What happens to the immature retroviruses after they are released from the host cell?
-The immature retroviruses undergo a series of chemical changes to become mature. Once mature, they are capable of infecting other cells and repeating the viral replication cycle.
What are the main steps in the retrovirus replication cycle?
-The main steps include: the retrovirus attaching to the host cell, reverse transcription of viral RNA into DNA, integration of viral DNA into the host cell’s genome, production of viral RNA and proteins, assembly of new viruses, and release of the newly formed viruses to infect other cells.
Outlines
🦠 Introduction to Retroviruses
In this introductory section, the speaker explains that retroviruses are a specific type of RNA virus, distinguished by their possession of the enzyme reverse transcriptase. This enzyme allows the virus to perform transcription in reverse, a process that will be explained in detail later. Additionally, retroviruses contain another key enzyme, integrase, which will play a significant role in the replication process. The structure of the retrovirus is described, highlighting the outer lipid envelope, the inner capsid, and the nucleic acid enclosed within.
🔄 Retrovirus Entry and Reverse Transcription
This part focuses on the retrovirus' initial entry into the host cell. The virus fuses with the cell membrane, allowing it to enter. The capsid of the retrovirus then dissolves, releasing enzymes and RNA into the host cell. Reverse transcription is initiated by reverse transcriptase, which uses viral RNA to create viral DNA. This process is unique to retroviruses and is crucial for their replication.
🔬 Integration of Viral DNA
The viral DNA created through reverse transcription enters the host cell's nucleus, accompanied by the integrase enzyme. Integrase's function is symbolized by scissors, as it cuts the host's DNA, allowing the viral DNA to integrate into the host genome. This combination of host DNA and viral DNA forms a 'provirus,' which will direct the host cell's machinery to produce viral components.
🧬 Viral RNA Replication
Once the viral DNA has integrated, the host cell begins to transcribe the viral DNA along with its own. Instead of producing its own RNA, the cell starts producing viral RNA. This happens repeatedly, creating multiple copies of viral RNA that will be used later to assemble new viruses.
🧪 Viral Protein Production
In this section, the viral RNA attaches to ribosomes in the host cell's cytoplasm. The ribosomes, which typically create proteins for the cell, now translate viral RNA into viral proteins, including reverse transcriptase, integrase, and capsid proteins. These proteins are crucial for assembling new retroviruses.
🧩 Assembly and Release of New Viruses
The viral proteins created by the ribosomes self-assemble into immature retroviruses. These newly formed viruses bud out of the host cell membrane and are released. Though initially immature, they undergo chemical changes to become mature retroviruses capable of infecting other cells and repeating the replication cycle.
🔁 Summary of Retrovirus Replication
The final part of the video recaps the retrovirus replication process. The retrovirus enters the host cell, reverse transcription occurs to produce viral DNA, which integrates into the host's DNA. The host cell then produces viral RNA and proteins, which self-assemble into new viruses. These newly formed retroviruses are released, allowing the cycle to repeat. Viewers are thanked for watching and encouraged to share their thoughts in the comments.
Mindmap
Keywords
💡Retrovirus
💡Reverse Transcriptase
💡Transcription
💡Integrase
💡Capsid
💡Provirus
💡Ribosome
💡Translation
💡Lipid Bilayer
💡Replication
Highlights
Retroviruses are a specific type of RNA virus that possess an enzyme called reverse transcriptase.
Reverse transcriptase allows retroviruses to perform reverse transcription, creating viral DNA from viral RNA.
The viral DNA created through reverse transcription is integrated into the host cell's DNA by an enzyme called integrase.
Integrase is responsible for cutting open the host DNA and integrating the viral DNA, forming a pro-virus.
The host cell's normal transcription process is hijacked, producing viral RNA instead of cellular RNA.
Viral RNA is used by the host cell's ribosomes to create viral proteins, such as reverse transcriptase and integrase.
The viral proteins produced in the cell self-assemble into immature retroviruses.
These immature viruses bud off from the host cell membrane and are released to infect new cells.
Over time, immature viruses undergo chemical changes to become mature retroviruses capable of repeating the cycle.
The retrovirus replication cycle begins when the virus attaches and enters the host cell, releasing its enzymes and RNA.
Once inside the host cell, the capsid of the retrovirus dissolves, releasing the viral enzymes and RNA.
During reverse transcription, viral RNA is used to build a molecule of viral DNA, reversing the usual flow of genetic information.
Viral RNA is repeatedly created during the normal transcription process, leading to multiple copies of viral RNA.
The process of translation allows the viral RNA to be read by the ribosome, resulting in the production of viral proteins.
Newly formed retroviruses are released from the host cell membrane, marking the completion of the replication cycle.
Transcripts
okay so in this video we're going to
discuss retroviruses so let's go ahead
and get started you know as far as
viruses go there are several different
categories and types of viruses but
retroviruses are a specific type of RNA
virus and what makes them so unique is
that they possess an enzyme by the name
of reverse transcriptase typically if
you if you look at molecules and if a
molecule ends with the letters ASE it's
some kind of enzyme and that's what
reverse transcriptase is now in the
named reverse transcriptase you know
reverse means to go backwards and when
you hear the word transcriptase perhaps
you think of the process of
transcription so when we get into this
video in a little bit what you're going
to see is the process of transcription
going backwards that'll be more clear
when we get further into the video so in
my picture here there is this red circle
labeled reverse transcriptase and
there's other enzymes in the retrovirus
as well one very important enzyme is a
enzyme called integrase and you'll
understand why it's called integrase
later notice how there's also an outer
envelope that surrounds the entire
retrovirus and also an inner capsid that
surrounds the nucleic acid and the
enzymes but what we're going to do is
we're going to look at the steps that a
retrovirus goes through in order to
replicate so you have the key in the
upper left hand corner so you know what
everything is in my animation so what
how this process begins is the
retrovirus will attach and then enter
into the host cell so here comes our
retrovirus and it's just attached to the
cell membrane of the host the outer
envelope of the retrovirus is a lipid by
a phospholipid bilayer so the to fuse
together and as they fuse together the
retrovirus is taken into the host cell
well now which have not watch
what happens to the yellow capsid the
yellow capsid is dissolved and begins to
break down
this releases the enzymes of the
retrovirus and the RNA nucleic acid of
the retrovirus so the next step is going
to be the process of reverse
transcription now normally when I hear
the word transcription I think of this a
DNA molecule is used to create an RNA
molecule
however retroviruses because they have
that enzyme called reverse transcriptase
are able to perform transcription in
reverse reverse transcriptase will
actually bind to the virus RNA and
perform reverse transcription the viral
RNA will be used to build a molecule of
viral DNA and eventually the enzyme
reverse transcriptase is degraded and
broken down but more importantly the
retrovirus has created viral DNA for
itself and you're going to see why
that's important right now so as we move
on to the next step the DNA of the virus
that was just created will actually
enter into the nucleus along with the
enzyme called integrates now there's a
reason I've drawn integrase to kind of
look like a pair of scissors here to be
symbolic of what it performs integrase
will actually cut open the DNA of the
host cell and it's called integrase
because it helps to integrate the DNA of
the virus into the DNA of the host cell
that's why it's called integrase and
what this creates is this combination of
host cell DNA and viral DNA that is
known as a pro virus and so now when we
look at the next step viral RNA will be
created each time the host cell
transcribes its DNA so inside the host
cell our enzyme
that will direct the normal process of
transcription which is a using DNA to
make a molecule of RNA so in the nucleus
here is an enzyme that the cell
possesses and it will do normal
transcription notice what it did though
it made a copy of not cell RNA it made a
copy of viral RNA and so this happens
many many times and here we have another
copy of viral RNA being created and I
think I have five of them in my
animation so there's a third one and
here's a fourth copy of viral RNA being
made and lastly a fifth copy of viral
RNA being made through the normal
transcription process and so now what
happens is we're going to see the
purpose of making all this viral RNA
keep in mind in the cytoplasm of a cell
cells possess ribosomes now they possess
many ribosomes I'm just showing one here
for simplicity so what happens is the
viral RNA attaches to a ribosome and
through the process of translation the
ribosome will read the viral RNA and
create viral proteins viral proteins
such as reverse transcriptase as the
process of as this process continues the
ribosome will continue to read other
viral RNAs and create integrase the
viral protein called integrase and so if
you see what's happening the cells own
ribosomes are creating parts for new
viruses and as this process continues
the ribosome also creates the capsid of
a virus the capsid of a virus is simply
made from protein and that's what the
ribosome builds the ribosome builds
proteins it just so happens that the
proteins belong to viruses instead of
important parts needed by our cells to
survive
and so eventually these viral proteins
that the cells own ribosome created will
self assemble into immature viruses so
here we have the viral proteins self
assembling into retroviruses into new
immature retroviruses and eventually
these these immature viruses are
released through the cell membrane so
notice how the cell membrane has began
to bud out and as the process continues
the cell membrane continues to butt out
and bulge out until eventually there you
go a retrovirus has been released now
the same thing will happen with the
other two retroviruses in the cell but
this is how new viruses are created that
will then be released to repeat the
cycle eventually these immature viruses
will go through a series of of chemical
changes to become mature but then
they'll be able to repeat the cycle and
infect other cells if we finish this
video with a quick summary of what we've
learned here's a retrovirus entering its
genetic material into a host cell and
then the the process of reverse
transcription is performed to make DNA
of the of the retrovirus that viral DNA
is then integrated into the the host
cell's DNA into the genome of the host
cell this process will then direct the
duplication in the creation of a whole
bunch of viral RNA and viral proteins
the viral RNA and proteins will self
assemble into new retroviruses that will
be released so this is the cycle of how
a retrovirus replicates I hope you found
this video helpful and thank you for
watching and place your comments in the
box below I'd like to hear what you
think
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