title: Drosophila Hindsight and mammalian RREB-1 are evolutionarily conserved DNA-binding transcriptional attenuators.
abstract: The Drosophila Hindsight (hnt) gene encodes a C2H2-type Zinc-finger protein, HNT, that plays multiple developmental roles including control of embryonic germ band retraction and regulation of retinal cell fate and morphogenesis. While the developmental functions of the human HNT homolog, RREB-1, are unknown, it has been shown to function as a transcriptional modulator of several tumor suppressor genes. Here we investigate HNT's functional motifs, target genes and its regulatory abilities. We show that the C-terminal region of HNT, containing the last five of its 14 Zinc fingers, binds in vitro to DNA elements very similar to those identified for RREB-1. We map HNT's in vivo binding sites on salivary gland polytene chromosomes and define, at high resolution, where HNT is bound to two target genes, hnt itself and nervy (nvy). Data from both loss-of-function and over-expression experiments show that HNT attenuates the transcription of these two targets in a tissue-specific manner. RREB-1, when expressed in Drosophila, binds to the same polytene chromosome sites as HNT, attenuates expression of the hnt and nvy genes, and rescues the germ band retraction phenotype. HNT's ninth Zinc finger has degenerated or been lost in the vertebrate lineage. We show that a HNT protein mutant for this finger can also attenuate target gene expression and rescue germ band retraction. Thus HNT and RREB-1 are functional homologs at the level of DNA binding, transcriptional regulation and developmental control.
authors.affiliation: Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8. Electronic address: liang.ming@utoronto.ca.
authors.forename: Liang
authors.initials: L
authors.lastname: Ming
authors.affiliation: Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8. Electronic address: ronit.wilk@utoronto.ca.
authors.forename: Ronit
authors.initials: R
authors.lastname: Wilk
authors.affiliation: Department of Biology, University of Waterloo, 200 University Avenue W, Waterloo, Ontario, Canada N2L 3G1. Electronic address: reed@uwaterloo.ca.
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Reed
authors.affiliation: Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8. Electronic address: howard.lipshitz@utoronto.ca.
authors.forename: Howard D
authors.initials: HD
authors.lastname: Lipshitz
mesh_terms: D000818:Animals; D001665:Binding Sites; D017124:Conserved Sequence / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004330:Drosophila / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008322:Mammals; D009024:Morphogenesis / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; C101743:RREB1 protein, human; D014157:Transcription Factors; C106513:peb protein, Drosophila
keywords: DNA-binding site; Hindsight; Polytene chromosome; RREB-1; Transcriptional attenuation; Zinc-finger