Molecular characterisation of the Polycomblike gene of Drosophila melanogaster, a trans-acting negative regulator of homeotic gene expression

Abstract

The Polycomblike gene of Drosophila melanogaster, a member of the Polycomb Group of genes, is required for the correct spatial expression of the homeotic genes of the Antennapaedia and Bithorax Complexes. Mutations in Polycomb Group genes result in ectopic homeotic gene expression, indicating that Polycomb Group proteins maintain the transcriptional repression of specific homeotic genes in specific tissues during development. We report here the isolation and molecular characterisation of the Polycomblike gene. The Polycomblike transcript encodes an 857 amino acid protein with no significant homology to other proteins. Antibodies raised against the product of this open reading frame were used to show that the Polycomblike protein is found in all nuclei during embryonic development. Antibody staining also revealed that the Polycomblike protein is found on larval salivary gland polytene chromosomes at about 100 specific loci, the same loci to which the Polycomb and polyhomeotic proteins, two other Polycomb Group proteins, are found. These data add further support for a model in which Polycomb Group proteins form multimeric protein complexes at specific chromosomal loci to repress transcription at those loci.

Multiple functions ofDrosophilaheat shock transcription factorin vivo

“…The single‐copy Drosophila hsf gene is located between the genes staufen ( stau ) and Polycomblike ( Pcl ) at cytological position 55A (Clos et al ., 1990; Lonie et al ., 1994). A Pcl mutation, Pcl P2 , was isolated by mobilizing a P‐element inserted in stau (Lonie et al ., 1994).…”

“…The single-copy Drosophila hsf gene is located between the genes staufen (stau) and Polycomblike (Pcl) at cytological position 55A (Clos et al, 1990;Lonie et al, 1994). A…”

“…Pcl mutation, Pcl P2 , was isolated by mobilizing a Pelement inserted in stau (Lonie et al, 1994). Using PCR and in situ hybridization analysis, we determined that the transposition event that generated the Pcl P2 mutation also deletes hsf.…”

Two distinct nuclear receptor interaction domains in NSD1, a novel SET protein that exhibits characteristics of both corepressors and coactivators

“…There are also four PHD fingers located N‐terminal to the SET domain of the Drosophila Trx protein and its human homolog (HRX/All‐1/MLL; Stassen et al ., 1995 and references therein; Figure 3A and C). In contrast, Ash1 contains a single C‐terminally located PHD finger (Figure 3A and C), whereas Pcl, the product of the Drosophila polycomb‐group gene Polycomb‐like , has two PHD fingers, but no SET domain (Lonie et al ., 1994; Figure 3C). Adjacent to the C‐terminus of the NSD1 PHD V , there is a sixth region rich in cysteine and histidine residues, which could correspond to a zinc finger‐like motif, however different from PHD fingers and other Cys‐rich motifs so far described (residues 2062–2103; Figure 2A).…”

“…PHDs with C4HC3 motifs have been described in a number of proteins, some of which are known to be implicated in chromatin-mediated transcriptional regulation (Aasland et al 1995). These include: (i) the Trx-G proteins Trx and Ash1, which in addition to a SET domain have, four PHDs and a single PHD, respectively; (ii) the Pc-G member, Polycomb-like (Pcl), which has two PHDs (Lonie et al, 1994); and (iii) the putative mediators of the ligand-dependent activation function AF-2 of nuclear receptors TIF1α and CBP/p300, which all have a PHD finger and a bromodomain (Glass et al, 1997 and references therein). TIF1α, as well as TIF1β which belong to the same gene family, interact specifically with the mammalian heterochromatinic proteins HP1α, MOD1 (HP1β) and MOD2 (HP1γ) (Le Douarin et al, 1996), whereas the CREB-binding protein CBP and p300 have an intrinsic histone acetyltransferase activity and interact with histone acetyltransferase (Bannister and Kouzarides, 1996;Ogryzko et al, 1996).…”