Binding profile comparison of Tritrorax-like across Drosophila species. Lijia Ma, Nicolas Negre, Matt Slattery, Rebecca Spokony, Sasha Ostapenko, Ryan Ptashkin, Jennifer Zieba, Kevin White. Institute for Genomics and Systems Biology, University of Chicago, Chicago, IL.

   PcG proteins and the counterpart TrxG proteins are key regulators to govern gene repress and active after the first wave of early embryonic repressors begin to disappear. Histone marks, like H3K27me3 and H3K4me3 have been proved to involve in PcG/TrxG regulation. However, it is still unclear how PcG/TrxG proteins were recruited to polycomb response elements (PREs) and work with histone marks then further regulate target genes activity. Here we identified binding profiles of Trithorax-like (Trl) in early embryo and White Prepapue in four Drosophila species (Drosophila melanogaster, Drosophila simulans, Drosophila yakuba and Drosophila pseudoobscura). The wide distribution of Trl peaks is consistent with its recruiting function, in which TrxG proteins function as antagonist to PcG proteins as well as general transcription activators. We observed the binding events of Trl are generally conserved across species, and the pair-wise conservations of non-melanogaster peaks relative to Dmel decrease along their evolutionary distance increasing. The conservation rates also drop with the distance between peaks and transcription starting sites indicating TSS-proxy binding events are more functionally essential. There is no significant difference in nucleotide divergence and motif quality between conserved peaks and species-unique peaks, but chromatin structures and co-factor availability might contribute to binding events gain or loss.