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Mol. Cell. Biol., 04 1996, 1813-1823, Vol 16, No. 4
K Certel, MG Anderson, RJ Shrigley and WA Johnson
Transcriptional regulators utilizing the POU domain DNA-binding motif have
been shown to form multi-protein complexes dependent on the POU domain
itself and its flexible recognition of various octamer sequence elements.
We have identified two variant POU domain recognition elements DFRE1 and
DFRE2, which are found within a 514-bp autoregulatory enhancer of the
Drosophila melanogaster POU domain gene drifter (dfr). Both elements are
capable of binding bacterially produced full-length DFR protein with high
affinity, although they differ in the 5'-to-3' orientation of POU-specific
and POU homeodomain subelements. When placed in dfr loss-of-function
genetic backgrounds, all expression of dfr-lacZ fusion genes under control
of the autoregulatory enhancer is dependent on DFR activity levels.
However, the complete enhancer sequence directs beta-galactosidase
expression in only a subset of cells which normally express the endogenous
DFR protein, including the middle pair of midline glias of the ventral
nerve cord, the oenocyte clusters, and all tracheal cells. In addition,
DFRE1 and DFRE2 exhibit separable tissue-specific functions when
independently disrupted or deleted. Disruption of DFRE1 function
specifically abolishes beta-galactosidase expression in the middle pair of
midline glias. Deletion of DFRE causes a specific loss of tracheal
expression, leaving oenocyte and midline glia expression intact. These
results suggest that dfr cell-specific autoregulation is determined by the
context of DFR POU domain binding within the enhancer, which is possibly
mediated by the formation of recognition element-specific heteromultimeric
complexes containing additional tissue-specific factors.
Copyright © 1996, American Society for Microbiology
Distinct variant DNA-binding sites determine cell-specific autoregulated expression of the Drosophila POU domain transcription factor drifter in midline glia or trachea
Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, 52242, USA.
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