Description:

Epigenetic Defense Mechanisms: Coping with Transposable Elements in the Drosophila Genome

The Center for Genetic Medicine of Northwestern University welcomes you to attend the Richard A. Scott, MD Lecture, featuring Sarah C. R. Elgin, PhD, Victor Hamburger Professor of Arts & Sciences, Professor of Biology, and Professor of Genetics, Washington University in St. Louis; and Investigator, Howard Hughes Medical Institute.

Eukaryotic genomes contain high levels of transposable elements (TEs) and their remnants, DNA that is commonly packaged for silencing in heterochromatin. Work in the fruit fly Drosophila melanogaster has suggested how such silencing occurs at the nucleosome level, utilizing an alternative pattern of histone modification with association of heterochromatin-specific proteins, notably HP1. This mechanism appears to be conserved from the yeast S. pombe to humans, with similarities in chromatin/genome organization as revealed by the modENCODE project (Ho et al. 2014 Nature 512:449-52). Correct targeting of heterochromatin formation is critical, as inadvertent silencing will lead to loss of gene function, with deleterious effects (example – triplet repeat mutations, such as Friedrich’s Ataxia). In flies, both the type and density of repetitious elements (primarily transposons) appear to be critical. Mapping experiments indicate that heterochromatin formation can be targeted by the presence of a transposable element (TE) remnant, 1360, as well as by simple repeats. Genetic analysis has shown that heterochromatic silencing targeted by 1360 is dependent on the RNAi machinery; we find that Piwi (the piRNA binding protein) is critical for HP1a deposition at some TEs. Piwi appears to play a role in setting up heterochromatin structure in the early embryo, but is not required to maintain silencing in the eye linage. Alternative mechanisms may be involved in targeting simple repeats. Further work will be needed to understand these complex systems, which are critical to maintaining the integrity of the genome.

The Scott Lecture Series is co-sponsored by Northwestern University's Driskill Graduate Program (DGP) in Life Sciences, part of the Lectures in Life Sciences series.

The Scott Lecture Series was created as an educational platform to appeal to the medical community of Northwestern University. It is funded under the generous bequest of Richard A. Scott, MD, a Northwestern University Medical School alum. After Dr. Scott passed away, his wife, Anne Lesak Scott, and family established the CGM lecture series in honor of Dr. Scott's lifelong interest in research.