Viktor Hamburger Lecture - Visualization of Transvection in Living Drosophila Embryos - Mike Levine
Mike Levine, Princeton University; "Visualization of Transvection in Living Drosophila Embryos"
Transcriptional enhancers regulate the on/off activities of target genes in response to a variety of cellular signals. The human genome is thought to contain hundreds of thousands of enhancers, ~10-20 enhancers per protein coding gene. For many years we have used the early embryo of the fruit fly Drosophila melanogaster to study the basic properties of enhancer DNAs. Past studies using traditional fixed tissue methods provided many insights into the spatial limits of gene expression, but only limited information about temporal dynamics. Live imaging methods provide new opportunities for understanding the timing of gene activity. The early Drosophila embryo is ideally suited for such studies, since the nuclei are organized in a simple grid along the surface of the egg. These studies identified transcriptional bursting as a common feature of gene expression. Bursts do not appear to be caused by unstable enhancer-promoter loops since a single enhancer can co-activate linked reporter genes in cis or in trans (transvection). I will discuss “transcription hubs” to explain these results. Transvection assays also provide insights into the proximity of enhancer-promoter interactions, and reveal a curious
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