A two-color bacterial two-hybrid system for selecting sequence-specific DNA-binding proteins via fluorescence activated cell sorting

Abstract

Proteins that recognize specific DNA sequences play a major role in many biological processes, and the ability to select or design novel DNA binding proteins could have a major impact on many areas of biotechnology and medicine. This thesis begins with background information on zinc finger DNA-binding proteins and on methods to select these proteins, and how they can be used to regulate endogenous human genes. Next, I describe a structural and biochemical study of a DNA-binding protein which demonstrates some of the complexities of the protein-DNA interface, and which highlights difficulties for designing sequence-specific proteins via a simple code. I then develop an experimental system (starting with a pre-existing bacterial two-hybrid selection system) which allows the selection of proteins based on their preference of one DNA site over another. I use this system to attempt to attenuate the affinity of a zinc finger protein without destroying its specificity. Finally, I describe an experiment in which I select a new domain that adds sequence specificity to a pre-existing protein from a library of completely random peptides.