RNA interference animation
Summary
TLDRThe video script delves into RNA interference, a process popularized by experiments involving double-stranded RNA in worms. It explains how RNA polymerase generates pre-mRNAs, which are processed into mature mRNAs and translated in the cytoplasm. The script highlights the role of microRNAs and RNA silencing pathways in gene regulation, antiviral defense, and the creation of small interfering RNAs (siRNAs) by Dicer. It also discusses the RNA-induced silencing complex (RISC), which cleaves target mRNAs, and the amplification mechanisms involving RNA-dependent RNA polymerase (RdRP), crucial for antiviral responses and gene regulation in organisms like plants, fungi, and worms.
Takeaways
- 🧬 RNA interference is a process where double-stranded RNA (dsRNA) is used to silence genes in a sequence-specific manner.
- 🐛 The technique was popularized by injecting dsRNA into a worm's gonad, which is a common method for introducing transgenes in worms.
- 🛡️ dsRNA blocks the expression of endogenous genes, which is an important tool for studying gene function.
- 📝 Gene transcription by RNA polymerase II generates pre-mRNAs that are processed into mature mRNAs, which are then transported to the cytoplasm for translation.
- 🔄 RNA can regulate endogenous gene expression through mechanisms involving microRNAs and other short regulatory RNAs.
- 🌿 In plants and other organisms, RNA can be activated by endogenous transposition and plays a role in antiviral defense.
- 🔪 Dicer, a member of the RNase III family, cleaves dsRNA into small interfering RNAs (siRNAs) with two-nucleotide 3' overhangs.
- 🤝 siRNAs form a ribonucleoprotein complex called RISC, which includes an argonaute protein with an RNAse H-like domain.
- ⚔️ RISC mediates the unwinding of the siRNA duplex, allowing a single-stranded siRNA to bind to and cleave target mRNA in a sequence-specific manner.
- 🚫 Cleaved mRNA is recognized as aberrant and destroyed, preventing translation and silencing gene expression.
- 🌱 In plants, aberrant RNA from RISC-mediated cleavage can serve as a template for RNA-dependent RNA polymerase (RdRP), generating more siRNAs.
- 🔄 Some organisms have an amplification step involving single-stranded siRNAs binding to target mRNAs and serving as primers for RdRP to synthesize the antisense RNA strand.
- 🌱 RNA spreading between cells is suggested to underlie germline transmission of RNA in worms and has been described in plants.
- 🐇 RNA spreading has not been described in mammals, indicating differences in RNA interference mechanisms across species.
Q & A
What is RNA interference and how was it popularized?
-RNA interference is a biological process where RNA molecules regulate gene expression. It was popularized by the work of researchers who injected long double-stranded RNAs into a worm's gonad, which blocked the expression of endogenous genes in a sequence-specific manner.
How do genes get transcribed in the cell?
-Genes are transcribed by RNA polymerase II, which generates pre-mRNAs that are then processed to form mature mRNAs.
What is the role of mRNA in the cell?
-mRNAs are transported from the nucleus to the cytoplasm where they serve as templates for protein synthesis through the process of translation.
What are microRNAs and how do they regulate gene expression?
-MicroRNAs are genomically encoded short regulatory RNAs that can regulate endogenous gene expression in organisms such as algae, worms, and flies.
How does RNA play a role in antiviral defense?
-In antiviral defense, double-stranded RNA from viruses is targeted for destruction by the RNA machinery, preventing viral replication and spread.
What is Dicer and how does it function in RNA interference?
-Dicer is a member of the RNase III family of double-stranded RNA-specific endonucleases. It recognizes and cleaves long double-stranded RNAs into small interfering RNAs (siRNAs) with two-nucleotide long 3' overhangs.
What is the RNA-induced silencing complex (RISC) and what does it include?
-The RNA-induced silencing complex (RISC) is a ribonucleoprotein complex that includes Slicer, an Argonaute protein with an RNA-binding domain. It mediates the unwinding and cleavage of target mRNAs.
How does the RISC complex mediate mRNA cleavage?
-RISC first mediates the unwinding of the siRNA duplex, and then a single-stranded siRNA that is coupled to RISC binds to a target mRNA in a sequence-specific manner. This binding mediates target mRNA cleavage by the Slicer protein.
What happens to the cleaved mRNA and how does it lead to gene silencing?
-The cleaved mRNA is recognized by the cell as aberrant and is destroyed, preventing translation from occurring and thus silencing the expression of the gene from which the mRNA was transcribed.
How does the RNA-dependent RNA polymerase (RdRP) contribute to RNA interference?
-RdRP uses the aberrant RNA resulting from RISC-mediated cleavage as a template for unprimed RNA synthesis, generating more double-stranded RNA, which serves as a substrate for Dicer activity, producing more siRNAs.
What is the significance of RNA spreading in the context of RNA interference?
-RNA spreading is a process that allows the RNA interference signal to move between cells, which is thought to underlie the germline transmission of RNA in worms and has also been described in plants.
Outlines
🧬 RNA Interference and Gene Regulation
This paragraph delves into the discovery and mechanism of RNA interference, a process that silences gene expression. It starts with the historical context of its discovery through the injection of double-stranded RNAs into a worm's gonad, which led to the blockage of endogenous gene expression. The paragraph explains the role of RNA polymerase II in generating pre-mRNAs, which are processed into mature mRNAs. It further discusses how microRNAs and other small regulatory RNAs can activate RNA interference. The central mechanism involves the cleavage of double-stranded RNAs by Dicer, an enzyme that generates small interfering RNAs (siRNAs) with two-nucleotide overhangs. These siRNAs form part of the RNA-induced silencing complex (RISC), which includes the 'slicer' protein. The RISC unwinds the siRNA duplex, and a single strand binds to a target mRNA, leading to its cleavage and subsequent destruction, thereby preventing translation and silencing the gene. The paragraph also touches on the role of RNA-dependent RNA polymerase (RdRP) in creating aberrant RNA from the cleaved mRNA, which can generate more siRNAs, and the amplification and spreading of RNA interference in organisms like plants and worms, but not in mammals.
Mindmap
Keywords
💡RNA interference
💡Double-stranded RNAs (dsRNAs)
💡Dicer
💡Small interfering RNAs (siRNAs)
💡RNA-induced silencing complex (RISC)
💡Slicer
💡Gene silencing
💡RNA-dependent RNA polymerase (RdRP)
💡Amplification
💡RNA spreading
💡Endogenous RNA mechanisms
Highlights
RNA interference was popularized by the injection of long double-stranded RNAs into a worm's gonad.
This method blocked the expression of endogenous genes in a sequence-specific manner.
Gene transcription by RNA polymerase II generates pre-mRNAs that are processed into mature mRNAs.
mRNAs are transported from the nucleus to the cytoplasm for translation.
RNA can regulate endogenous gene expression through microRNAs in various organisms.
RNA can be activated by endogenous transposition in plants and insect cells.
RNA plays a role in antiviral defense by targeting viral double-stranded RNA for destruction.
Long double-stranded RNAs are recognized and cleaved by Dicer, a member of the RNAse III family.
Cleavage by Dicer creates small interfering RNAs (siRNAs) with two-nucleotide long 3' overhangs.
siRNAs form the RISC (RNA silencing complex), which includes the Slicer protein.
RISC mediates the unwinding of the siRNA duplex and targets mRNA for cleavage.
The cleaved mRNA is recognized as aberrant and destroyed, preventing translation.
In plants, aberrant RNA from RISC-mediated cleavage serves as a template for RNA-dependent RNA polymerase (RdRP).
RdRP uses the aberrant RNA template for unprimed RNA synthesis, generating more siRNAs.
RNA interference involves an amplification step with single-stranded siRNAs priming RdRP.
The specificity of RNA interference is sensitive to natural sequence variation.
RNA spreading between cells is thought to underlie germline transmission of RNA in worms.
RNA spreading has been described in plants but not in mammals.
Transcripts
RNA interference was popularized by work
in
cagans when long double stranded rnas
were injected into a worm's gonad a
standard way of introducing trans genes
into worms they blocked the expression
of endogenous genes in a sequence
specific
manner in UK cariot most protein coating
genes are transcribed by RNA polymerase
2 which generates pre-mrnas that are
then processed to form mature
mrnas these mrnas are then transported
from the nucleus to the cytoplasm where
they are
translated RNA I can regulate endogenous
gene
expression
RNA can be set in motion by genomically
encoded short regulatory rnas known as
micro
rnas in algae worms and flies RNA can be
activated by endogenous
transposition in plants and cultured
insect cells RNA also has a role in
antiviral defense in which viral doubl
stranded RNA
are targeted for Destruction by the RNA
Machinery when long doubl stranded rnas
enter a cell they are recognized and
cleaved by daiser which is a member of
the rna's 3 family of double stranded
RNA specific
endonucleases cleavage by daer creates
short double stranded rnas that are
characterized by two nucleotide long
three prime
overhangs these are called small
interfering or si
rnas si rnas can form a
ribonucleoprotein complex called risk or
RNA silencing complex this complex
includes slicer an argonut protein with
an RNA H like domain called
peeee risk first mediates the unwinding
of the sna duplex a single stranded sna
that is coupled to risk then binds to a
Target mRNA in a sequent specific
manner The Binding mediates Target mRNA
cleavage by slicer the sight of the
cleavage falls in the middle of the
region of sirna
complementarity the cleaved mRNA can be
recognized by the cell as being aberant
and then destroyed this prevents
translation from occurring silencing the
expression of the gene from which which
the MRNA was
transcribed in Plants the aberant RNA
that results from the risk mediated
cleavage can also serve as a template
for RNA dependent RNA polymerase or
rdrp this process relies on unprimed RNA
synthesis in which the aberant RNA is
used as a
template the resulting double stranded
RNA is a substrate for dacer activity
which generates more si rnas in some
organisms with endogenous RNA mechanisms
for example fungi plants worms and
mammals RNA also involves another
amplification
step in this step singl stranded sirnas
not associated with risk bind to their
Target mrnas in a sequent specific way
and serve as a primer for rdrp to
polymerize the antisense RNA
strand such specificity is intrinsically
sensitive to Natural sequence
variation the double stranded RNA
molecule that is created serves as a
substrate for daiser which cuts it into
snas in turn these can either unwind and
Prime RNA dependent RNA
polymerization or together with risk
mediate the cleavage of Target
mrnas this amplification coupled with
RNA spreading between cells is thought
to underline germline transmission of
RNA in worms RNA spreading has also been
described in Plants but not in
mammals
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