Introduction

Imagine that we could develop a protein that was able to target an exact sequence of DNA, allowing some subsequent manipulation - what range of applications would there be?

• We could deactivate specific genes, by attaching nucleases to these targeting proteins.
• We could create synthetic promoter regions, and target them with proteins attached to transcriptional activation or repression machinery.
• We could target the insertion of new genes to specific areas, where they would be unlikely to have any undesired side-effects.

Such a set of proteins, then, would be relevant to the fields of synthetic biology (Haynes & Silver, 2009; Lu et al., 2009), metabolic engineering (Grotewold, 2008), targeted gene therapy (Carroll, 2008), and would be widely useful as research tools for genomic manipulations.

Referred to here as sequence-specific DNA binding proteins, their broad applicability and usefulness is hard to overstate. Fittingly, a great deal of effort has been spent on their development. Three key examples will be covered in this blog: the bZIP family, zinc finger proteins, and in particular, the TAL proteins, which are emerging as the most easily engineered variety.