Determining the structural mechanism of how single-stranded DNA binding proteins bind DNA

Abstract

Single stranded DNA binding proteins (SSB) play a major role in cellular DNA processing events such as replication, recombination and repair and are central to maintaining the integrity of our genome. These processes require the DNA double helix to unwind, exposing less stable and highly vulnerable regions of single stranded DNA (ssDNA). SSB proteins bind ssDNA via a highly conserved oligonucleotide-binding (OB)domain and function to temporarily bind and protect exposed ssDNA generated during these events. The vital role of SSBs is evident from their ubiquitous presence in all forms of life.In the recent years, high resolution DNA-bound structures of bacterial SSBs and the eukaryotic Replication Protein A (RPA) were published, significantly enhancing our understanding of the molecular mechanism of DNA binding by SSBs. Although the structure of the archaeal SSB from Sulfolobus solfataricus (SsoSSB) has been solved, the DNA binding details of this protein have not been elucidated until now. This thesis reveals the structural basis of ssDNA recognition by SsoSSB and provides the first look into how archaeal SSBs bind ssDNA at the structural level.Two novel human SSBs, hSSB1 and hSSB2 were recently discovered. Prior to this, RPA was the only known SSB in humans, therefore this discovery has provided a new dimension to our understanding of DNA processing events in our cells and is now aprevailing topic of interest. The main function of the hSSBs appears to be central to arange of DNA repair pathways. However, irrespective of their precise function in DNA repair, both homologs are primarily involved in binding ssDNA, and act very early inthe damage response. This has provided us with the opportunity to study hSSB1 and hSSB2 as suitable targets to shut down highly active DNA repair processes in tumourcells. In this thesis, I present the structural basis of DNA binding by hSSB1 and hSSB2which will ultimately complement the development of hSSB inhibitors for the use innovel anti-cancer therapeutics.

Date of Award	2017
Original language	English