Lymphoid expression and TATAA binding of a human protein containing an
Antennapedia homeodomain
LJ Baier, MC Hannibal, EW Hanley and GJ Nabel
Department of Internal Medicine, Howard Hughes Medical Institute,
University of Michigan Medical Center, Ann Arbor 48109-0650.
In an effort to identify human proteins that bind to the TATAA box, a
lambda gt-11 expression library was screened with a radiolabeled DNA probe
containing 12 copies of the TATAA sequence. A cDNA encoding a specific
TATAA binding protein was isolated and found to contain a homeobox domain
identical at 59 of 60 residues to the Drosophila Antennapedia (Antp)
homeodomain, as well as another conserved motif found in homeotic genes,
the homeo-specific pentapeptide. Although this and other Antp-like homeobox
proteins have been described previously in neuronal cells and fibroblasts,
we report the expression of this gene in lymphoid cells. This cDNA,
isolated from a B-cell library, hybridizes to a 1.6-kb messenger RNA in
several T- and B-cell lines, and the expected protein was identified in
Jurkat T-lymphoid cells by Western blot analysis. The DNA binding
specificity of this human Antp clone was analyzed using single-base
mutations of the TATAA sequence. The first thymidine, as well as the last
three bases (TAA), were important for homeobox binding. Finally, the
function of the highly conserved homeospecific pentapeptide protein region
was investigated in both the human and Drosophila Antp proteins. The
homeospecific pentapeptide region was not required for DNA binding, and
Drosophila Antp proteins mutated in the pentapeptide region were able to
transactivate the Ubx promoter in Schneider L2 cells, in contrast to a
homeodomain mutation, suggesting an alternative function for the
homeospecific pentapeptide in homeotic genes. Because the human Antp TATAA
binding protein is expressed in both lymphoid and non-lymphoid cells, we
suggest that this homeobox gene has evolved a more general transcriptional
regulatory function in higher eukaryotic cells.
Volume 78,
Issue 4,
pp. 1047-1055,
08/15/1991
Copyright © 1991 by The American Society of Hematology
