Following are the most popular programmable DNA-binding domains that allow you to design a custom transcription factors, which can bind to your desired DNA sequence. These can then be used as a transcriptional activators/repressors/nucleases/epigenetic modifiers based on the effector module fused to the programmed DNA-binding module:

1. CRISPR-Cas9/dCas9

2. Transcription Activator-Like Effectors (TALEs)

3. Zinc-fingers

The above order ranks the platforms from easy to difficult in designing.

Hope this is useful to you.

All the best,

Manjunatha