Drosophila Reptin and other TIP60 complex components promote generation of silent chromatin

Histone acetyltransferase (HAT) complexes have been linked to activation of transcription. Reptin is a subunit of different chromatin remodeling complexes, including the TIP60 HAT complex. In Drosophila, Reptin also co-purifies with the Polycomb group (PcG) complex PRC1, which maintains genes in a transcriptionally silent state. We demonstrate genetic interactions between reptin mutant flies and PcG mutants, resulting in mis-expression of the homeotic gene Scr. Genetic interactions are not restricted to PRC1 components, but are also observed with another PcG gene. In reptin homozygous mutant cells, a Polycomb response element-linked reporter gene is de-repressed, whereas endogenous homeotic gene expression is not. Furthermore, reptin mutants suppress position-effect variegation (PEV), a phenomenon resulting from spreading of heterochromatin. These features are shared with three other components of TIP60 complexes, namely Enhancer of Polycomb, Domino and dMRG15. We conclude that Drosophila Reptin participates in epigenetic processes leading to a repressive chromatin state as part of the fly TIP60 HAT complex rather than through the PRC1 complex. This shows that the TIP60 complex can promote the generation of silent chromatin.

Key Words: Drosophila, Polycomb group, chromatin, position-effect variegation

Online ISS 1091-6490
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