when we use dCas- KRAB + gRNA inorder to methyate a specific part of DNA, how many gRNA is needed per nucleotide? is there a formula or not? The question is that.@Mar
Hi Sara, I don't think you will find a formula to that Q. It is very likely depends on chromatin architecture of the region you are working with. In general, my understanding is that CRISPR system does not work very efficiently when transcriptional regulation is concerned, (at least for activation), and the more you can use the better. You could tile all you enhancer with close by sgRNA, in such a way that they don't interfere with each other. Here you can block activity of your enhancer with bound CRISPR complexes as well (this is known effect for promoters at least). Of cause initiating formation of repressed chromatin is even better. So my thoughts are the more the better, except that you have to think about off-targets, and through out suspected bad sgRNAs.