Appointment period: 3/14/2012 to 3/13/2014

Project

Characterizing the Effect Dyskeratosis Congenita-Causing TIN2 Mutations have on Telomerase Activity

The ends of linear eukaryotic chromosomes are composed of highly repetitive DNA sequences referred to as telomeres. Telomeres are replenished by telomerase, a multi-subunit reverse transcriptase that uses its RNA component as a template to add telomeric sequence to the ends of chromosomes. In most human somatic cells, telomerase is inactive. In contrast, telomerase is highly active in germ, stem, and cancer cells. In humans, the telomeric sequence is protected by the shelterin complex, which is composed of six subunits: TRF1, TRF2, RAP1, TPP1, POT1, and TIN2. These components can protect the telomeres from being recognized as damaged DNA and are also believed to regulate the activity of telomerase at the telomeres. The shelterin component TIN2 binds to TRF1, TRF2, and TPP1, tethering these proteins within the shelterin complex at telomeres. Although TIN2 can be co-precipitated with telomerase core components through its interaction with TPP1, increased levels of full length TIN2 leads to slight telomere shortening. Heterozygous mutations within the TIN2 gene have been identified in patients with Dyskeratosis Congenita (DC), an inheritable disease that leads to bone marrow failure. One commonality among patients with DC is that they have abnormally short telomeres and defects in telomere biology. It is currently unclear why mutations within TIN2 lead to extremely shortened telomeres in DC patients. In my postdoctoral study, I want to elucidate the mechanism by which TIN2 regulates telomere length and how TIN2’s function is altered in patients with Dyskeratosis Congenita. In particular, I want to analyze the relationship between TIN2 and telomerase and determine how TIN2’s interaction with other proteins may alter TIN2’s function. I will create human cell lines, which will help provide a clean genetic model to study TIN2 functions in cultured human cells. These cell lines will also help determine the mechanism by which TIN2 mutations lead to the shortened telomeres in patients with Dyskeratosis Congenita. The knowledge obtained may ultimately help us find a successful treatment for these patients.