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Mol. Cell. Biol., 01 1997, 482-494, Vol 17, No. 1
L Cavarec, S Jensen, JF Casella, SA Cristescu and T Heidmann
By transfection experiments, we previously identified a 72-bp enhancer
sequence within the Drosophila copia retrotransposon which is involved in
the control of the transcription level of this mobile element in cells in
culture. Gel shift assays with nuclear extracts from Drosophila
hydei-derived DH-33 cells further demonstrated specific interactions of at
least two nuclear factors with this enhancer sequence. Using this sequence
as a probe for the screening of an expression cDNA library that we
constructed from DH-33 cells RNA, we have isolated a cDNA clone encoding a
110-kDa protein with features common to those of known transcription
factors; these include a two- zinc-finger motif at the C terminus, three
glutamine-rich domains in the presumptive activation domain of the protein,
and an N-terminal domain which shares homology with the Bric-a-brac,
Tramtrack, and Broad- Complex BTB boxes. The precise DNA recognition
sequence for this transcription factor has been determined by both gel
shift assays and footprinting experiments with a recombinant protein made
in bacteria. The functionality of the cloned element was demonstrated upon
transcriptional activation of copia reporter genes, as well as of a minimal
promoter coupled with the identified target DNA sequence, in cotransfection
assays in cells in culture with an expression vector for the cloned factor.
Southern blot and nucleotide sequence analyses revealed a related gene in
Drosophila melanogaster (the lola gene) previously identified by a genetic
approach as involved in axon growth and guidance. Transfection assays in
cells in culture with lola gene expression vectors and in situ
hybridization experiments with lola gene mutants finally provided evidence
that the copia retrotransposon is regulated by this neurogenic gene in
D.melanogaster, with a repressor effect in the central nervous systems of
the embryos.
Copyright © 1997, American Society for Microbiology
Molecular cloning and characterization of a transcription factor for the copia retrotransposon with homology to the BTB-containing lola neurogenic factor
Unite de Physicochimie et Pharmacologie des Macromolecules Biologiques, CNRS URA147, Institut Gustave Roussy, Villejuif, France.
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