Structure, Function and Evolution of the TelomeraseRNA Subunit in Plants

Texas A&M Research Foundation, College Station TX

Investigators

Abstract

Project Summary The overall goal of this project is to characterize the structure, function and interactions of the telomerase RNA (TER) subunit in Arabidopsis. Telomerase is a ribonucleoprotein reverse transcriptase that uses TER as a template to direct the synthesis of telomeric DNA onto chromosome ends. Preliminary data unexpectedly revealed that Arabidopsis, unlike all other model organisms, has two TER subunits, TER1G7 and TER5G2. The RNAs display different levels of expression, in vitro biochemical properties and protein binding partners. Because maintenance of telomere tracts is essential to sustain genome integrity and to promote cell proliferation in all eukaryotes, elucidating the functions and interactions of the two Arabidopsis TERs is likely to provide new insight into telomerase regulation and evolution. For Objective 1, genetic and transgenic approaches are proposed to examine the functions of TER1G7 and TER5G2 in vivo. The relative contributions of the two RNAs in telomere maintenance will be studied as well as the effect of altering the ratio of the two RNAs. Objective 2 is to study TER1G7 and TER5G2 interactions with TERT by reconstituting active RNP particles in vitro. These studies will investigate the dimerization state of the RNP and its relationship to enzyme activity. In vivo experiments are also proposed to study RNP composition and oligomerization in Arabidopsis organs with different levels of telomerase activity. This work will address fundamental aspects of telomerase function and regulation in plants, and may also shed light on the physiological advantages of duplicating and diversifying a key component of the telomerase enzyme. Intellectual Merit of the Proposed Study The intellectual merit of this project is that it will provide new insight into the structure, function and evolution of TER, a core component of the telomerase holoenzyme. The novel aspect of this work is that it couples the genetic tractability of Arabidopsis with in vitro biochemistry to explore the function and dynamic interactions of two TER subunits. The results may not only reveal underlying mechanisms contributing to the dramatic differences in telomerase RNP biogenesis and composition observed in single-celled organisms and in metazoa, but also may uncover new modes of telomerase enzyme regulation. Broader Impacts The multi-disciplinary nature of this work provides participants with expertise in cutting edge RNA and protein biochemistry, plant biology and genetics. The studies to be performed employ new tools to investigate telomerase RNA gene duplication and diversification. In particular, since molecular evolution approaches have not been applied to the study of telomeres in any model system, the potential impact of this work on the field is high. Over the past 16 years, the principal investigator has trained a large number of postdoctoral fellows, graduate and undergraduate students. She has given numerous lectures for high school students and teachers, and undergraduate and graduate student organizations, including the 2003 Texas A&M University Women in Science and Engineering Ethel Ashworth-Tsutsui Memorial Lecture. The principal investigator has a long-standing interest in laboratory management and in 2009 will be an integral participant in an inaugural "best practices in laboratory leadership" workshop to take place in the Texas A&M Mays Business School. In 2002 the principal investigator was an Instructor for the Burroughs Wellcome Fund/Howard Hughes Medical Institute Laboratory Management Course, and in 2005 she presented a lecture entitled "Leading a Laboratory" for the Women in Science organization at the Annual Meeting for the Society for Free Radical Biology and Medicine in Austin, Texas.