Association of trxG and PcG proteins with the bxd maintenance element depends on transcriptional activity.
Polycomb group (PcG) and trithorax group (trxG) proteins act in an epigenetic fashion to maintain active and repressive states of expression of the Hox and other target genes by altering their chromatin structure. Genetically, mutations in trxG and PcG genes can antagonize each other's function, whereas mutations of genes within each group have synergistic effects. Here, we show in Drosophila that multiple trxG and PcG proteins act through the same or juxtaposed sequences in the maintenance element (ME) of the homeotic gene Ultrabithorax. Surprisingly, trxG or PcG proteins, but not both, associate in vivo in any one cell in a salivary gland with the ME of an activated or repressed Ultrabithorax transgene, respectively. Among several trxG and PcG proteins, only Ash1 and Asx require Trithorax in order to bind to their target genes. Together, our data argue that at the single-cell level, association of repressors and activators correlates with gene silencing and activation, respectively. There is, however, no overall synergism or antagonism between and within the trxG and PcG proteins and, instead, only subsets of trxG proteins act synergistically.
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Svetlana
S
Petruk
Sheryl T
ST
Smith
Yurii
Y
Sedkov
Alexander
A
Mazo
D000483:Alleles; D000818:Animals; D030801:Animals, Genetically Modified; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics* / Q000378:metabolism; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D044127:Epigenesis, Genetic; D005456:Fluorescent Dyes / Q000378:metabolism; D017344:Genes, Insect; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D007211:Indoles / Q000378:metabolism; D063150:Polycomb Repressive Complex 1; D034622:RNA Interference; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D019076:Transgenes
D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; D005456:Fluorescent Dyes; D018398:Homeodomain Proteins; D007211:Indoles; C066770:Pc protein, Drosophila; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; C512571:trx protein, Drosophila; C007293:DAPI; D063150:Polycomb Repressive Complex 1