Transcriptional response elements in the promoter of CYP6B1, an insect P450 gene regulated by plant chemicals.
Papilio polyxenes, a lepidopteran continually exposed to toxic furanocoumarins in its hostplants, owes its tolerance to these compounds to the transcriptional induction of the CYP6B1 gene encoding a P450 capable of metabolizing linear furanocoumarins, such as xanthotoxin, at high rates. Transient expression of various lengths of wild-type and mutant CYP6B1v3 promoter in lepidopteran Sf9 cells defines a positive element (XRE-xan) from -136 to -119 required for both basal and xanthotoxin-inducible transcription and a negative element from -228 to -146 that represses basal transcription. Fusion of the CYP6B1v3 XRE-xan element to the Drosophila melanogaster Eip28/29 core promoter indicates that the XRE-xan functions in conjunction with its own core promoter but not with a heterologous core promoter. Sequence searches of the CYP6B1v3 proximal promoter region revealed a number of putative elements (XRE-AhR, ARE, OCT-1, EcRE, C/EBP, Inr) sharing sequence similarity with those in other regulated vertebrate and insect promoters. Mutation of TGAC nucleotides shared by the overlapping EcRE/ARE/XRE-xan indicates that this sequence is essential for basal and regulated transcription of this gene. Mutagenesis in the non-overlapping region of the EcRE indicates it modulates basal transcription. These findings are incorporated into a working model for regulation of this toxin-inducible promoter.
Petersen
Rebecca A
RA
Department of Entomology, 320 Morrill Hall, 505 South Goodwin Avenue, University of Illinois, Urbana, IL 61801, USA.
Niamsup
Hataichanoke
H
Berenbaum
May R
MR
Schuler
Mary A
MA
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis / Q000235:genetics*; D001483:Base Sequence; D002478:Cells, Cultured; D011564:Furocoumarins / Q000737:chemistry / Q000494:pharmacology; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007915:Lepidoptera; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016296:Mutagenesis; D011401:Promoter Regions, Genetic / Q000187:drug effects; D020218:Response Elements / Q000502:physiology*; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic; D014162:Transfection
D011564:Furocoumarins; D001189:Aryl Hydrocarbon Hydroxylases; C465261:cytochrome P-450 CYP6B1 (butterfly)