I will be discussing two approaches to
reduce or eliminate the expression of gene A.
RNA interference is a
sequence-specific method to silence
genes by introducing small
double-stranded RNAs. dsRNA binds to
the protein Dicer and Dicer cleaves dsRNA into smaller fragments which can be
siRNAs or miRNAs.
siRNAs and miRNAs bind with proteins to form a RISC complex, that
will base pair with mRNA either
inhibiting translation are causing the degradation of mRNA.
This is a RNA based
therapeutic which is used to treat transthyretin mediated amyloidosis in adult patients. Amyloidosis is characterized by
the deposit of abnormal protein called
amyloid, in multiple organs of the body where it should not be.
Here, the siRNA is
designed to correspond to a specific
gene target but the siRNA is
synthesized by drug-like properties
which provide stability and conjugation
for delivery. Modified siRNA penetrates
the cell membrane and harnesses the RNAi mechanism.
Gene silencing then achieves a therapeutic effect.
The CRISPR cas system is a prokaryotic
immune defense mechanism to cleave
invading DNA but has recently been used
for eukaryotic gene editing. The first
step involves adaptation. The system
starts invading phage and plasmid DNA
segments into CRISPR loci. The system is
adapted to target other genomes to allow
for genome editing. The second step is
RNA processing. Here, the host transcribes
and processes CRISPR loci to
generate mature CRISPR RNA containing
both CRISPR repeat elements and the
integrated spacer elements. The last step
is RNA interference. crRNA detects
foreign DNA and forms a complex with the
foreign DNA. Here, the system uses guide
RNA to cut a specific unwanted sequence
and it pairs with the DNA we want to cut
out. Another DNA sequence must be added
that carries the appropriate sequence we
wish to implicate. Here in this example
we have our target DNA. We also have our
guide DNA which guides the cas 9
system to pair with it and cut out the
unwanted sequences that you see.
CRISPR has also been used to target HIV
Pause to read!
If I wanted to reduce or eliminate that
expression in gene A, I would choose the
CRISPR approach because RNAi could
interfere with the wrong RNA. CRISPR
targets a specific sequence and replaces that sequence with the desired
DNA sequence, meaning it can induce both insertions and deletions. CRISPR could
also target many genes at once.
High specificity and variability makes
the CRISPR approach more favorable.
