Project Summary/Abstract
Telomere length plays a pivotal role in cancer and age-related degenerative disease. Telomeres are made of
simple tandem repeats, added by the enzyme telomerase, to establish a length distribution. A mechanistic
understanding of the forces that regulate telomere length is needed to develop approaches to disease. Current
models for how the telomere length equilibrium is maintained suggest that ends with fewer telomere repeats
are more frequently elongated than ends with many repeats implying that all telomeres are regulated around
the same length distribution. We developed a nanopore sequencing method to measure telomere length in
yeast at the nucleotide level. Surprisingly, we found that each telomere had a distinct length distribution that
was maintained over hundreds of cell divisions. This discovery requires that current models for length
regulation be revised. In this proposal we detail specific experiments to test mechanisms that may modify the
length distribution at specific chromosome ends: 1. Subtelomeric sequences 2. Telomere
transcription/telomere RNA (TERRA), and the Sir2/3/4 histone modification complex. We will use
computational approaches to determine if specific sequence motifs are associated with long or short
telomeres, and we will systematically delete DNA binding sites to test their role. We will use nanopore RNA
sequencing to study the long non-coding RNA TERRA, and test whether the RNA, or the action of transcribing
the telomere play a role in end-specific telomere lengths. Finally, we will test the role of the histone
deacetylase Sir2 and the interaction of Sir4 with Ku in determining end-specific telomere lengths. These
experiments will implicate or rule out the specific factors that establish different length distributions.
Understanding molecular mechanism(s) that influence telomere length distributions will set the stage to
specifically manipulate telomere length. Because mechanisms of telomere length regulation are conserved
across species, our experiments will set the stage for approaches to alter telomere length to treat human
disease.