InteractiveFly: GeneBrief

tre-1; tre-2; tre-3: Biological Overview | References

Homeotic genes contain cis-regulatory trithorax response elements (TREs) that are targeted by epigenetic activators and transcribed in a tissue-specific manner. The transcripts of three TREs located in the Drosophila homeotic gene Ultrabithorax mediate transcription activation by recruiting the epigenetic regulator Ash1 to the template TREs. TRE transcription coincides with Ubx transcription and recruitment of Ash1 to TREs in Drosophila. The SET domain of Ash1 binds all three TRE transcripts, with each TRE transcript hybridizing with and recruiting Ash1 only to the corresponding TRE in chromatin. Transgenic transcription of TRE transcripts restores recruitment of Ash1 to Ubx TREs and restores Ubx expression in Drosophila cells and tissues that lack endogenous TRE transcripts. Small interfering RNA-induced degradation of TRE transcripts attenuates Ash1 recruitment to TREs and Ubx expression, which suggests that noncoding TRE transcripts play an important role in epigenetic activation of gene expression (Sanchez-Elsner, 2006). Please note that the Sanchez-Elsner paper has been retracted (see retraction report)

The identity of cells in metazoan organisms is established during development and mitotically propagated throughout the entire life cycle. Phylogenetically highly conserved protein families of epigenetic regulators determine the fate of developing cells by establishing and maintaining mitotically stable gene expression programs. In Drosophila, members of the trithorax group (trxG) of epigenetic regulators maintain active transcription states, whereas members of the Polycomb group (PcG) maintain repressed transcription states. Many epigenetic regulators control gene expression by establishing transcriptional competent or silent chromatin structures. Several epigenetic activators [Trx, Trithorax-relatedd (Trr)] and repressors (Enhancer of zeste) are lysine-specific histone methyltransferases (HMTs) and contain a SET domain, the catalytic hallmark motif of HMTs. Methylation of lysine residues in histones H3 and H4 has been correlated with epigenetic activation [Lys⁴ in H3 (H3-K4)] and repression [Lys⁹ and Lys²⁷ in H3 (H3-K9)] (Sanchez-Elsner, 2006).

Sanchez-Elsner, T., Gou, D., Kremmer, E. and Sauer, F. (2006). Noncoding RNAs of trithorax response elements recruit Drosophila Ash1 to Ultrabithorax. Science 311(5764): 1118-23. PubMed ID: 16497925. Please note that the Sanchez-Elsner paper has been retracted (see retraction report)

date revised: 13 December 2007

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