Seminar：Establishment of Zygotic Transcription and Chromatin Organization in the Early Drosophila Embryo

Speaker：Dr.CHEN Kai

                   Postdoctoral Fellows

                   Stowers Institute for Medical Research, USA

Host：Dr.ZHANG Zhihua

Time：10:00-11:00 am, June 2

Location:First-floor, Conference Room, BIG, CAS

Abstract:

Massive zygotic transcription begins during the Drosophila midblastula transition when the cell cycle of the dividing egg slows down. A few genes are transcribed before this stage but how this differential activation is accomplished is still an open question. We have performed ChIP-Seq experiments on tightly staged Drosophila embryos and show that massive recruitment of RNA polymerase II (Pol II) with widespread pausing occurs de novo during the midblastula transition. However, ~100 genes are strongly occupied by Pol II before this timepoint with little pausing. This global change in Pol II pausing is correlated with distinct core promoter elements and transcription factors. In particular, TATA-containing promoters are enriched in the ~100 genes that are expressed very early in Drosophila embryogenesis, whereas TATA-containing promoters are less frequent in genes that are expressed later. In addition, ChIP-Seq experiments showed that the promoters of genes that are expressed very early are associated with different combinations of general transcription factors than those of genes that are expressed later. Together, our results suggest that promoters are differentially used during the Zygotic Genome Activation, presumably by recruiting different general transcription factors to assemble the transcriptional machinery.