Tom Volpe
Title: Assistant Professor
Research area: Heterochromatin  Formation in Higher Eukaryotes
Degree: Ph.D.
Voice: 312.503.5391
Fax: 312.503.7912
e-mail: t-volpe2@northwestern.edu

Detailed research description:
We use the fission yeast Schizosaccharomyces pombe as a model to study heterochromatin formation in higher eukaryotes. Heterochromatin was originally identified cytologically as densely staining chromosomal regions in interphase nuclei and has since been implicated in such diverse cellular processes as dosage compensation, imprinting, stem cell function, chromosome segregation, DNA repair and recombination. The mechanisms by which cells establish and maintain these heterochromatic domains, however, are not fully understood. Our studies in Schizosaccahromyces pombe have shed some light on this problem. We found that centromeric silencing and normal chromosome segregation in S. pombe depend on the RNAi machinery. Our data also reveal that centromeric repeats, previously thought to be transcriptionally inactive, are actually expressed. These heterochromatic centromeric transcripts are rapidly processed by RNAi into small fragments that may provide sequence specificity for targeting silencing machinery to centromeres. Similarities between RNAi dependent gene silencing in S. pombe and silencing phenomena in other organisms, such as X-chromosome inactivation in mammals, suggest that RNAi may be a fundamental process for maintaining genomic stability and regulating gene expression in higher eukaryotes.
 

Representative publications:

Martienssen R., Volpe T., Lippman Z., Gendrel A.V., Kidner C., Rabinowicz P., and Colot V. (2003)     Transposable elements, RNA interference and the origin of heterochromatin. RNAi: A Guide to                    Silencing. Hannon G, Editor. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY.

Volpe T.A., Schramke V., Hamilton G., White S.A., Teng G., Martienssen R.A., and Allshire R.C. (2003)      RNA Interference is Required for Normal Centromere Function. Chromosome Research 11(2):137-46.

Volpe T.A., Kidner C., Hall I.M., Teng G., Grewal S.I., Martienssen R.A. (2002) Regulation of Heterochromatic Silencing and Histone H3 Lysine-9 Methylation by RNAi. Science 297:1833-7.