The long term goal of the parent grant is to understand the regulation of telomerase in baker's yeast. We wish to extend the original aims of this grant to the analysis of telomerase in a second model system, the fission yeast, S. pombe. Thus, we are requesting funds under NOT-OD-09-058 with Notice Title: NIH announces the availability of recovery act funds for competitive revision applications. In work supported by the parent grant, my lab has pioneered the use of chromatin immuno-precipitation to study S. cerevisiae telomerase. Here we propose to use chromatin immuno-precipitation to determine if S. pombe telomerase is regulated by both the cell cycle and by telomere length, as it is in S. cerevisiae. We will also use both a three-hybrid screen and mass spectrometry to identify new components of the S. pombe telomerase holoenzyme. We also propose a microscopic/cell biological approach that relies on bimolecular fluorescent complementation to study the interaction and regulation of the multi-protein shelterin complex that protects the ends of S. pombe chromosomes from degradation and regulates their access to telomerase. We wish to expand our telomere research to S. pombe because multiple aspects of telomere maintenance in this organism are more similar to humans than is true for S. cerevisiae. For example, the recently discovered S. pombe shelterin complex is strikingly similar to the complex at human telomeres. Finally, there has been no systematic genetic screen for S. pombe telomerase components so it is possible that some of its subunits have not been identified. PUBLIC HEALTH RELEVANCE: The regulation of telomerase is highly relevant to human health. Telomerase expression, which is upregulated in the vast majority of human tumors, is associated with their unlimited growth potential. In addition, telomerase is expressed but at very low levels in human stem cells, and even modest reductions in this level can lead to stem cell failure with dire effects on life span.