T-box transcription factors are important developmental regulators in all multicellular organisms, and the level of T-box gene expression is often crucial for their function. The C. elegans
tbx-2 gene encodes a conserved T-box transcription factor essential for development of ABa-derived pharyngeal muscles. The
tbx-2 promoter is active in pharyngeal precursors prior to formation of the pharyngeal primordium, as well as in a subset of neurons and in bodywall muscle. We are examining regulation of the
tbx-2 promoter to understand how T-box gene expression is regulated. We have found that
tbx-2 promoter activity is repressed by the NF-Y heterotrimeric CCAAT-binding complex. RNAi knockdown of
nfya-1 ,
nfyb-1 or
nfyc-1 results in strong ectopic expression of
tbx-2::gfp in gut and seam cells of late larva e and adults. In comparison, RNAi knockdown of
nfya-2 results in weak ectopic expression of
tbx-2::gfp . Together, these results suggest an NF-Y complex containing the A-1, B-1, and C-1 subunits repress
tbx-2 expression. In the
nfya-1(
ok1174) mutant, the
tbx-2 promoter is ectopically expressed more strongly and at earlier stages than NF-Y RNAi animals. Mutation of two CCAAT sites in the
tbx-2 promoter result in ectopic expression of the
tbx-2 promoter in seam and intestinal cells, strongly suggesting NF-Y is a direct repressor of
tbx-2 expression. To identify additional mechanisms regulating
tbx-2 expression we are also characterizing the
tbx-2 promoter region. We have identified a
tbx-2 transcriptional enhancer that is necessary and sufficient for expression in the embryonic pharynx. This enhancer contains sequences conserved in other Caenorhabditis species, and we are currently examining the function of these sequences.