Abstract
The Polycomb group (PcG) proteins have been implicated in epigenetic transcriptional repression in development, stem cell maintenance and in cancer. The chromodomain protein Polycomb (Pc) is a key member of the PcG. Pc binds to the histone mark, trimethylated histone 3 lysine 27 (H3K27me3), to initiate transcriptional repression. How PcG proteins are recruited to target loci is not fully understood. Here we show that the Drosophila SERTA domain protein Taranis (Tara) is involved in transcriptional regulation of Pc target genes. Embryos lacking Tara exhibit a partial homeotic transformation of cuticular the segments, a phenotype associated with the loss of Pc function. Moreover, Drosophila embryos homozygous for a tara hypomorphic allele also misexpress engrailed, a Pc-regulated gene, and this phenotype is associated with the loss of Pc binding to the cis response element in the engrailed enhancer. In relation to that, Pc recruitment is reduced on the salivary gland polytene chromosomes and specifically at the engrailed locus. These results suggest that Tara might be required for positioning Pc to a subset of its target genes.
Highlights
Epigenetic mechanisms dictate the developmental fates of cells in an organism
We used a transgenic assay system that contains a boundary element for the iab-7 Polycomb response element (PRE) from the Bithorax complex (BX-C) locus called Frontoabdominal 7 (Fab-7) [8,23,24] It regulates selector gene Abdominal-B in the wild type context
We examined whether Tara is required for Pc binding to en Polycomb Response Element (PRE) with Chromatin IP (ChIP)
Summary
Epigenetic mechanisms dictate the developmental fates of cells in an organism. Two important classes of proteins, implicated in this dynamic and multifaceted process, are highly conserved members of the Polycomb (PcG) and Trithorax (TrxG) groups [1]. The PcG proteins are transcriptional repressors whereas the TrxG proteins counteract transcriptional silencing by antagonizing PcG function. The PcG proteins include members such as Enhancer of zeste and Polycomb (Pc). Enhancer of zeste is a SET domain methyl transferase that methylates histone 3 at lysine 27 to create trimethylated histone 3 lysine 27 (H3K27me3), a repressive chromatin mark. Pc is a chromodomain protein and key member of the PcG, which recognizes and binds to the H3K27me, leading to silencing of its target genes [2]
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