Activation by Myc in Drosophila embryos
Different from targets of repression by Myc, targets of activation are expressed at low levels during embryogenesis. These targets are also affected by Polycomb and Pho, which help maintain their low level of expression in the absence of ectopic Myc.
These genes differ from Myc targets of repression in their chromatin modifications. They are methylated at H3 lysine 27, as are targets of repression, but they are also methylated at H3 lysine 4, which is a hallmark of active chromatin (ref). Other than our work, this combination of H3 K27 and H3 K4 methylation has only been found in mammalian embryonic stem cells, at developmentally regulated loci (ref).
We are interested in how Myc selects its targets of activation and repression, and how they differ as embryogenesis proceeds. We have several projects pursuing different aspects of this question, such as: is Myc able to repress a target at one time in embryogenesis and activate that same target later in embryogenesis? What are the consequeces of Myc activation of other activators and/or repressors in downstream Myc activity? How do levels of chromatin-binding repressors and/or activators affect Myc function throughout embryogenesis? Our graduate student Abid will pursue one of these questions, and many others are available as projects for future post-docs and graduate students!
