Terace M. Fletcher 

Assistant Professor
of Biochemistry and Molecular Biology

Ph.D. (1994) University of Texas

Health Science Center

Chromatin structure: telomere
maintenance and transcriptional regulation

Tel: (305) 243-6297, Fax: (305) 243-3955

tfletcher@med.miami.edu

Research Interests:

The eukaryotic genome is organized into complex DNA-protein macromolecular assemblies known as chromatin. Chromatin has both an architectural and regulatory function in the nucleus. Our laboratory is interested in two processes influenced by chromatin structure: telomere maintenance and transcription.

Telomere Chromatin Structure. Telomeres, specialized nucleoprotein complexes at the end of chromosomes, have a crucial role in genomic stability. Disruption of telomere structure induces cell growth arrest or death. Cancer cells, unlike most normal somatic cells, maintain stable telomeres through the activation of the telomere-specific DNA polymerase, telomerase.

Our lab is particularly interested in the structural features of telomere higher-order assemblies and the mechanisms by which different telomere configurations are formed. Possible influences on telomere structure are: telomerase activity, telomere length, association of telomere binding and DNA repair proteins, and DNA structure.

To structurally and biochemically characterize telomere chromatin, we are reconstituting model telomeres in vitro. We use these model telomeres to determine recruitment of telomere binding and DNA repair proteins under certain conditions. We are also interested in the effects of telomere structure on functions such as telomerase activity and chromosome end protection. Finally, we are investigating the biochemical and hydrodynamic properties of telomere higher-order structures. One hydrodynamic method we will focus on is a unique agarose gel electrophoresis technique. This technique allows us to analyze surface electrical charge density and solution structure of large macromolecular DNA/protein assemblies from either purified components or in complex mixtures. We are applying this technique to study the structure of native telomeres isolated from nuclei.

Chromatin structure and transcription. It is well established that the same promoter sequence in different chromatin contexts has diverse responses to cellular signals. The biochemical mechanisms by which nucleosomes, the fundamental units of chromatin, exert their influence is under intense investigation. However, the role of chromatin higher-order structures in transcriptional activation is still largely unexplored. The goal of my lab is to simultaneously analyze the structural characteristics of chromatin and transcriptional activation under various reaction conditions.

Specifically, we are interested in the reciprocal relationship between transcription factors and their chromatin targets. Our approaches include reconstituting promoters and coding regions into chromatin in vitro and analyzing protein binding, chromatin remodeling, and transcriptional activation. We are also characterizing the solution structure of these chromatin fibers both reconstituted in vitro and isolated from cells.

Selected Publications

1. Baker, A., Fu, Q, Lindsay, S.M. and Fletcher, T.M. (2008) Interactions of the Myb-Like TRF2 DNA Binding Domain with Nucleosomal Array Fibers: An Analytical Agarose Gel Electrophoresis Investigation. (in prep)

2. Pedroso, I. and Fletcher, T.M. (2008) Effect of the TRF2 N-terminal and TRFH regions on Telomeric G-quadruplex Structures and Single-Strand Assimilation. (in prep)

3. Khan S.J., Fletcher, T.M., Pham, S., and Vazquez-Padron. (2008) ROS-Induced DNA Damage and Senescence in Vascular Smooth Muscle Cells (in prep)

4. Khan S.J., Wei, Y., Fletcher, T.M., Pham, S., and Vazquez-Padron. (2008) The Role of Vascular Smooth Muscle Cell Senescence in Injury-Induced Vascular Remodeling (in prep)

5. Baker, A., Fu, Q, Lindsay, S.M. and Fletcher, T.M. (2008) Nucleosomal Fiber Compaction and Self-Association by TTAGGG Repeat Factor 2 N-terminus. (in prep)

6. Khan S.J., Yanez, G., Saldeen, K., and Fletcher, T.M. (2007) Interactions of TRF2 with Model Telomeric Ends. Biochem Biophys Res Comm. 363: 22-50.

7. Pedroso, I.M., Duarte, L. F., Yanez, G., Burkewitz, K., and Fletcher, T.M. (2007) Sequence Specificity of Intra- and Intermolecular G-quadruplex Formation by Human Telomeric DNA Biopolymers 87:74-84.

8. Pedroso, I.M., Duarte, L.F., Yanez, G., Baker, A, and Fletcher, T.M. (2007) Induction of Parallel Human G-quadruplex Structures by Sr²⁺ Biochem Biophys Res Comm. 358:298-303.

9. Yanez, G.H, Khan, S.J., Locovei, A.M. Pedroso, I.P. and Fletcher T.M. (2005) DNA Structure-Dependent Recruitment of Telomeric Proteins to Single-stranded/Double-stranded DNA junctions Biochem Biophys Res Comm. 328: 49-56.

10. Fletcher, T.M. Telomerase: A Potential Therapeutic Target for Cancer (2005) Expert Opin. Ther. Targets, 9: 457-469.

11. Fletcher, T.M. (2003) Telomere Higher Order Structure and Genomic Instability IUBMB Life, 55:443-9

HONORS AND PROFESSIONAL ACTIVITIES

American Society for Cell Biology

American Association for Cancer Research