RVDs in a particular TALE recognizes different bases. So change in RVDs results in change in sequence specificity. 9 TALEs don't copolymerize. Only two TALEs with different RVDs bind to two adjacent sides of Fok1 recognition sequence. You're explanation is pretty much wrong.
Nidhya Joseph TALES from Xanthomonas has a DNA binding domain and an activator domain which allows it to regulate the activity of certain genes in it's host. The DNA binding domain has 30 repeats of 33-35 amino acid residues. Out of these 35 residues, residue number 12 and 13 are variable in the repeats and thus they are called repeat variable diresidue. These two amino acids are responsible for recognition of a single nucleotide in DNA. Amino acids NI at RVDs recognizes adenine, NG recognizes thymine, HD recognizes cytosine and NN recognizes adenine or guanine. So if you know the sequence of your DNA then you can design TALENS that bind to your specific sequence by changing the amino acids at 12 and 13th position of each repeat. In this way the talen can bind to your sequence and the DNA cleavage domain of Fok1 fused to the DNA binding domain of TALE can cleave the DNA. Generally two TALENS have to be coexpressed in a cell, one that binds upstream of the cleavage site and one that binds downstream. When the two will bind, two Fok1 domains come in vicinity and cleave the DNA molecule. The cleaved DNA can now be joined by non-homologous end joining which is an error prone double stranded break repair process , leading to incorporation of mutations in your desired sequence of interest.
Can you please elaborate? I did not get what exactly was stated wrong here..
Also how are both the TALEs and REN -eg. Fok 1 made so specific for a particular sequence? Both the TALES are different sequences right? Are there any chances of both these TAL effectors binding to each other..?
It is actually Fok1 (or capital i as a Greek number instead of "1"). For more information regarding its discovery please go to the following link published by the first researcher discovered it: http://www.ncbi.nlm.nih.gov/pubmed/6282705
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