NEXT GENERATION GENOME EDITING TECHNOLOGIES Next-Generation-Genome-Editing-Technologies | Page 5

The zinc finger proteins are vast family of proteins that have made themselves useful in numerous
ways in biological system. All the Znf found have one thing in common and that is the presence
of at least one zinc ion which is required for the coordination of all functional domains present
in Znf. The Cys2His2 motif of Znf recognizes the specific nucleotide triplet in the alpha helix and
another domain of Znf is that of a nuclease which acts like a sequence specific endonuclease
that works to binds and break DNA at specific positions. As said previously, it has two domains,
where one of the domains binds to DNA and comprises of eukaryotic transcription factors along
with the zinc finger whereas the second domain is comprised of a nuclease FokI enzyme involved
in breakdown of DNA (catalytic).
Later, another nuclease TALEN was discovered which began to compliment ZNFs domain and
was considered a perfect gene editing tool for years. TALENs are combinations of transcription
activator-like (TAL) proteins and a FokI nuclease. TAL proteins are made of repeating motifs
which are 33-34 amino acids long with two variable positions that have a perfect recognition for
unique nucleotide.
Source: https://www.jci.org/articles/view/72992/figure/2