UC San Diego

p73 is a sequence-specific transcription factor that belongs to the p53 family. It plays an important role in cell development and regulation, and initiating cell cycle arrest and apoptosis under cellular stresses. In p53 family proteins, p53 is considered as "the guardian of genome" with a primary role of tumor suppressor. However, mutations in p53, particularly in DNA-binding domain (DBD), are found in 50% of human cancers while p73 is rarely mutated. Therefore, it has been suggested that p73 can replace the functions of p53 mutants. The overall domain architecture of p53 family is similar with highly conserved DBD among the family members. The goal of this thesis is to study the DNA binding properties of p73 DBD using analytical ultracentrifugation and fluorescence anisotropy. Chapter 1 introduces transcription regulation, the p53 protein family and its pathway, and p73 isoforms. Chapter 2 studies the minimum length of DNA required for p73 DNA binding which has showed that p73DBD binds to a minimum 6 bp half-site as a dimer. Chapter 3 studies the p73 DNA binding specificity at each nucleotide position within the consensus half-site. In agreement with the previous crystal structures, the results have indicated that the cytosine and the guanine at position 4 are the most critical nucleotides in the consensus sequence. In addition, the p73 DNA binding affinity is salt concentration dependent. Chapter 4 described the expression and purification of p73 isoforms in order to further study p73 DNA binding property in the full-length content in the future