Emmanuel Skordalakes, Ph.D.

Assistant Professor
Gene Expression and Regulation Program
215-495-6884, Office
215-898-2202, Lab

Introduction

In recent years several links have begun to emerge between the integrity of eukaryotic chromosome ends, known as telomeres, and both cancer and aging. Studies from several research laboratories have identified proteins involved in replicating and regulating telomere length and stability; however, the function of these telomere maintenance factors and their role in human disease are far from fully established. The long-term goal of the Skordalakes laboratory is to understand how telomeric complexes protect chromosome ends and mediate their replication and apply this information in pursuit of anticancer therapies.

Research Summary

The focus of our research lies with protein nucleic acid assemblies that participate in the replication and maintenance of eukaryotic chromosome ends, called telomeres. Telomeres protect chromosomes from gradual length erosion, prevent end-to-end fusions and recombination, and promote proper chromosome partitioning during meiosis. The goal of our research is to elucidate the mechanism of telomere replication by the specialized DNA polymerase, telomerase and understand how telomere-binding proteins regulate telomerase activity and protect chromosome ends. We would also like to understand how a specific group of telomere binding proteins promote homologous chromosome pairing, an essential step in eukaryotic cell division during meiosis. The lab primarily uses structural methods coupled with biophysical and biochemical methods to study the above systems.

Telomere replication

The canonical eukaryotic replication machinery is unable to replicate the ends of linear chromosomes due to the properties of the enzyme that carries out this reaction. If not addressed, the cell would lose valuable genetic information in every cell division, leading to genomic instability, senescence and cell death. Cells have been able to overcome this problem by possessing a specialized DNA polymerase called telomerase, which adds short oligonucleotide repeats at the end of linear chromosomes using an integral RNA component as template. Our long-term goal is to obtain the high-resolution structure of the telomerase holoenzyme. Structural data will be subsequently used to design a host of biochemical and biophysical experiments, all of which will help us elucidate the mechanism of telomere replication by telomerase.

Telomerase regulation and telomere maintenance

Although telomere extension by telomerase is essential for the viability of the cell, regulation of this process is essential to prevent cell immortality and cancer. Furthermore the linear ends of chromosomes have to be protected from degradation and recombination. The newly synthesized telomeric DNA serves as a platform that recruits DNA-binding proteins that serve to regulate telomerase activity and protect chromosome ends. In human telomeres several well-characterized proteins, called TRF1, TRF2, and POT1, carry out this process. Two proteins, called TIN2 and PIP1, mediate the recruitment and proper assembly of the above telomere-binding proteins on telomeric DNA. Our goal is to understand how TIN2 and PIP1 promote TRF1, TRF2, and POT1 binding to telomeric DNA and how this in turn regulates telomerase activity and protects chromosome ends from been recognized as DNA strand breaks.

Chromosome Partitioning

Meiosis in eukaryotic cells increases diversity in the offspring by converting a diploid cell to a haploid gamete while promoting the distribution of genetic information via homologous chromosome pairing. During meiosis prophase I, homologous chromosome pairs are tethered to the nuclear envelope by the chromosome telomeres via their interaction with telomere binding proteins. Preliminary data suggests that telomere clustering to the nuclear envelope brings homologous chromosome pairs into close proximity thus reducing the volume and complexity of the homology search. Thus, telomere-led chromosome organization, otherwise known as bouquet formation, facilitates homologous pairing and restricts irregular chromosome pairing during meiosis. The lab will study the events that lead to tethering of eukaryotic chromosome ends to the nuclear envelope in an attempt to explain how this process facilitates the proper alignment of homologous chromosomes prior to cell division.

Selected Publications

1. Andrew J. Gillis, Anthony P. Schuller and Emmanuel Skordalakes: Structure of the Tribolium castaneum telomerase catalytic subunit TERT.Nature 455:633-637, 2008.

2. Susan Rouda and Emmanuel Skordalakes; Structure of the RNA-Binding Domain of Telomerase: Implications for RNA Recognition and Binding; Structure, Vol 15:1403-1412, 2007

3.  Skordalakes, E and Berger, JM.: Structural insights into RNA-dependent ring closure and motor domain activation by the Rho transcription termination factor. Cell 127:553-64, 2006.

4.  Skordalakes E, Brogan AP, Park, SB, Kohn, H, and Berger JM.: Structural mechanism of  inhibition of the Rho transcription termination factor by the antibiotic icyclomycin. Structure 13:99-109, 2005.

5.  Daganzo SM, Erzberger JP, Lam WM, Skordalakes E, Zhang R, Franco AA, Brill SJ, Adams PD, Berger JM, Kaufman PD.: Structure and function of the conserved core of histone deposition protein Asf1. Curr Biol. 13:2148-58, 2003.

6.  Skordalakes E, and Berger JM.: Structure of the Rho transcription terminator: mechanism of mRNA recognition and helicase loading. Cell 114:135-146, 2003 (Accompanying Minireview, Cell, 114:157-159, 2003).

7.  Hansen CL, Skordalakes E, Berger JM, Quake SR.: A robust and scalable microfluidic metering method that allows protein crystal growth by free interface diffusion. Proc Natl Acad Sci USA 99:16531-6, 2002.