Abstract
Polycomb group (Pc-G) proteins act to keep homeotic genes stably and heritably silenced during Drosophila development. Here, it is shown that Polycomb (Pc), one of the Pc-G proteins, acts as a transcriptional silencer in Drosophila embryos if tethered to reporter genes by the DNA binding domain of GAL4 (i.e. as a GAL-Pc fusion protein). The results suggest that silencing by GAL-Pc requires the C-terminal portion of Pc, but not the chromodomain. If a pulse of Gal-Pc is provided, synthetic reporter genes are repressed, though only transiently. In contrast, reporter genes containing homeotic gene sequences remain stably and heritably silenced in a Pc-G gene-dependent fashion, even when GAL-Pc is no longer present. This implies that GAL-Pc recruits Pc-G proteins to DNA and suggests that maintenance of silencing requires the anchoring of Pc-G proteins to specific cis-regulatory sequences present in homeotic genes. The extent of DNA over which the Pc-G machinery acts is quite selective, as silencing established on one enhancer does not necessarily 'spread' to a juxtaposed synthetic enhancer.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP-Binding Cassette Transporters*
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Animals
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Base Sequence
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Crosses, Genetic
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DNA / metabolism
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DNA-Binding Proteins / genetics
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Drosophila / embryology
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Drosophila Proteins*
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Enhancer Elements, Genetic / genetics
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Eye Proteins*
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Fungal Proteins / genetics
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Gene Expression Regulation, Developmental / physiology*
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Genes, Homeobox / genetics
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Genes, Reporter / genetics
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Homeodomain Proteins*
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Insect Hormones / genetics
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Juvenile Hormones / genetics
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Juvenile Hormones / physiology
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Models, Genetic
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Molecular Sequence Data
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Point Mutation / genetics
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Polycomb Repressive Complex 1
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Promoter Regions, Genetic / genetics
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Proteins / metabolism
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Proteins / physiology*
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Recombinant Fusion Proteins / biosynthesis
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Recombinant Fusion Proteins / physiology*
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Saccharomyces cerevisiae Proteins*
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Transcription Factors*
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Transcription, Genetic / physiology*
Substances
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ATP-Binding Cassette Transporters
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DNA-Binding Proteins
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Drosophila Proteins
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Eye Proteins
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Fungal Proteins
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GAL4 protein, S cerevisiae
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Homeodomain Proteins
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Insect Hormones
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Juvenile Hormones
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Pc protein, Drosophila
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Proteins
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae Proteins
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Transcription Factors
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Ubx protein, Drosophila
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hb protein, Drosophila
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w protein, Drosophila
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DNA
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Polycomb Repressive Complex 1