Transcriptional silencing of homeotic genes in Drosophila.
Homeotic genes are subject to transcriptional silencing, which prevents their expression in inappropriate body regions. Here, we shall focus on Drosophila, as little is known about this process in other organisms. Evidence is accumulating that silencing of Drosophila homeotic genes is conferred by two types of cis- regulatory sequences: initiation (SIL-1) and maintenance (SIL-M) elements. The former contain target sites for transient repressors with a highly localised distribution in the early embryo and the latter for constitutive repressors that are likely to be present in all cells. We discuss how SIL-1 elements may cooperate with SIL-M elements to promote formation of a silencing complex. We propose that this complex consists of specific non-histone proteins, the so-called Polycomb group proteins, and that it is anchored at SIL-M elements and at the promoter.
Bienz
M
M
MRC Laboratory of Molecular Biology, Cambridge, England.
Müller
J
J
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000648:ultrastructure; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D017344:Genes, Insect; D006570:Heterochromatin / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology; D063150:Polycomb Repressive Complex 1; D011506:Proteins / Q000502:physiology; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic
C062393:Abd-B proteins, Drosophila; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D006570:Heterochromatin; D018398:Homeodomain Proteins; C066770:Pc protein, Drosophila; D011506:Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C066177:Ubx protein, Drosophila; C061245:hb protein, Drosophila; D063150:Polycomb Repressive Complex 1