Functional Studies of TRF2 and its Interacting Proteins in Maintaining Telomere Length and Integrity

Abstract

<p>The ends of eukaryote chromosomes, a region called the telomeres, plays a critical role in maintaining genome stability. With each round of mitotic division the telomeres erode until a critically short length is reached, which signals the cell to permanently stop dividing. This is recognized as a contributing factor to ageing and the onset of age related diseases. Telomere repeat binding factor 2 (TRF2), is an important telomere DNA binding protein that has an essential role in protecting telomeres from being recognized as DNA breaks, however it has also been implicated in other aspects of telomere maintenance, such as telomere replication and telomere transcription. TRF2 acts as a protein hub for the recruitment of a number of telomere associated proteins involved in telomere maintenance, and it has been shown to be heavily modified by numerous types of post-translational modification. We demonstrate that TRF2 is methylated on arginine residues in its N-terminal region by protein arginine methyltransferase 1 (PRMT1) and that this arginine methylation is important for proper telomere maintenance. We further demonstrate that methylated TRF2 is a component of the nuclear matrix and has a distinct staining pattern in senescent cells. The importance of telomeres to ageing is exemplified by previously reported observations that defects in telomere maintenance are a common characteristic to numerous premature ageing disorders. We show that the premature ageing disorder, Cockayne Syndrome has an underlying defect in telomere maintenance. Approximately 80% of Cockayne Syndrome patients have mutations in the Cockayne syndrome group B (CSB) protein. We identified a novel interaction between TRF2 and CSB. The work presented in this thesis characterizes these novel interactions and gives new insight into the function of TRF2 in telomere maintenance.</p>