Locus-specific requirements for Spt5 in transcriptional activation and repression in Drosophila.
Segmental patterning in Drosophila relies on a cascade of transcription factors that subdivide the embryo into successively more precise domains. We have identified a missense mutation (W049) in the gene encoding the transcriptional elongation factor Spt5 (reviewed in ) which, when homozygous in the maternal germ line, leads to defects in segmental patterning of the embryo. W049 alters the C-terminal domain of Spt5 and affects its activity in vitro, impairing its abilities to confer sensitivity to the transcriptional inhibitor DRB and to stimulate transcription at limiting nucleotide concentrations. In vivo, W049 shows locus-specific effects on transcription: expression of gap genes remains wild-type, but striped patterning of the primary pair-rule genes even-skipped and runt is disrupted. even-skipped stripes are broadened in the mutant embryos indicating that Spt5 is likely to be a direct, negative regulator of this target gene. Our results suggest control of transcriptional elongation by repressors contributes to striped gene expression in the embryo. By contrast, expression of heat shock-induced proteins is reduced in the mutant embryos. These results provide genetic evidence for Spt5 function during heat shock induction and demonstrate that Spt5 acts both positively and negatively on transcription in vivo depending on context.
Jennings
Barbara H
BH
Developmental Genetics Laboratory, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom.
Shah
Sheetal
S
Yamaguchi
Yuki
Y
Seki
Masayuki
M
Phillips
Roger G
RG
Handa
Hiroshi
H
Ish-Horowicz
David
D
D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics*; D004252:DNA Mutational Analysis; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018869:Heat-Shock Response / Q000235:genetics; D018398:Homeodomain Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D020125:Mutation, Missense / Q000235:genetics; D009687:Nuclear Proteins; D018807:Polymorphism, Single-Stranded Conformational; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics*; D035602:Transcriptional Elongation Factors / Q000235:genetics*
D002868:Chromosomal Proteins, Non-Histone; D017931:DNA Primers; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D035602:Transcriptional Elongation Factors; C052837:eve protein, Drosophila; C080833:run protein, Drosophila; C069940:SPT5 transcriptional elongation factor