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Today, I would like to talk about siRNA on and off-target activity.
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When double stranded RNA is introduced into
the cells with a so natural Drosha/Dicer independent pathway,
or artificially cell introduction of chemicals synthesize dsRNAs,
it needs to be processed and enter in very complex protein complex called RISC.
As there is multiple forms of RISC available.
What is most important to understand that it's not a form of a RISC complex,
but rather in degree complementarity between siRNA loaded RISC complex and a target,
which defined mechanism of action.
If it's perfect complementarity,
the target is being cleaved and this is we will call
for purpose of today presentation, on target activity.
And then partial complementarity especially multiple partial
complementarity within other genes resulting translational inhibition,
and recently has demonstrated some mRNA degradation as well.
So first, I would like to focus on sRNA on target activity where perfect homology
between loaded RISC complex and a target result in cleavage mRNA and Gene Silencing.
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As siRNA function is defined by complex interaction with a protein machinery,
it's possible to speculate that
there might be some features within siRNA which makes
it interact better with a protein machinery and function better.
To be able to identify those features,
we realize that we need to have unbiased database,
where siRNA sequence is correlate or
correlated with siRNA functionality inside of cells.
And to be able to develop this completely unbiased database,
we decided to use an approach which called siRNA walking.
So, what is siRNA walks?
SiRNA walks is a collection or sets of siRNAs which
overlap in their sequence composition by 18 out of 19 base pairs.
So, we just shift siRNA targeting position one base pair at a time.
What we can see on this slide is systematic analysis of siRNA functionality,
