Remarkable site specificity of local transposition into the Hsp70 promoter of Drosophila melanogaster.
Heat-shock genes have numerous features that ought to predispose them to insertional mutagenesis via transposition. To elucidate the evolvability of heat-shock genes via transposition, we have exploited a local transposition technique and Drosophila melanogaster strains with EPgy2 insertions near the Hsp70 gene cluster at 87A7 to produce numerous novel EPgy2 insertions into these Hsp70 genes. More than 50% of 45 independent insertions were made into two adjacent nucleotides in the proximal promoter at positions -96 and -97, and no insertions were into a coding or 3'-flanking sequence. All inserted transposons were in inverse orientation to the starting transposon. The frequent insertion into nucleotides -96 and -97 is consistent with the DNase hypersensitivity, absence of nucleosomes, flanking GAGA-factor-binding sites, and nucleotide sequence of this region. These experimental insertions recapitulated many of the phenotypes of natural transposition into Hsp70: reduced mRNA expression, less Hsp70 protein, and decreased inducible thermotolerance. The results suggest that the distinctive features of heat-shock promoters, which underlie the massive and rapid expression of heat-shock genes upon heat shock, also are a source of evolutionary variation on which natural selection can act.
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia.
Victoria Y
VY
Shilova
David G
DG
Garbuz
Elena N
EN
Myasyankina
Bing
B
Chen
Michael B
MB
Evgen'ev
Martin E
ME
Feder
Olga G
OG
Zatsepina
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D017344:Genes, Insect; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010641:Phenotype; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D017931:DNA Primers; D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; D012333:RNA, Messenger