Transcriptional silencing by the Polycomb protein in Drosophila embryos.
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.
Müller
J
J
MRC Laboratory of Molecular Biology, Cambridge, UK.
D018528:ATP-Binding Cassette Transporters; D000818:Animals; D001483:Base Sequence; D003433:Crosses, Genetic; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D004330:Drosophila / Q000196:embryology; D029721:Drosophila Proteins; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005136:Eye Proteins; D005656:Fungal Proteins / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D005801:Genes, Homeobox / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics; D018398:Homeodomain Proteins; D007301:Insect Hormones / Q000235:genetics; D007605:Juvenile Hormones / Q000235:genetics / Q000502:physiology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D017354:Point Mutation / Q000235:genetics; D063150:Polycomb Repressive Complex 1; D011401:Promoter Regions, Genetic / Q000235:genetics; D011506:Proteins / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000502:physiology*
D018528:ATP-Binding Cassette Transporters; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D005136:Eye Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D018398:Homeodomain Proteins; D007301:Insect Hormones; D007605:Juvenile Hormones; C066770:Pc protein, Drosophila; D011506:Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; C061245:hb protein, Drosophila; C059254:w protein, Drosophila; D004247:DNA; D063150:Polycomb Repressive Complex 1