Wj. Chen et al., CHARACTERIZATION OF HUMAN E4BP4, A PHOSPHORYLATED BZIP FACTOR, Biochimica et biophysica acta, N. Gene structure and expression, 1264(3), 1995, pp. 388-396
In this report we described the isolation of transcription factor E4BP
4 by lambda gt11 expression cloning using a probe containing the CRE/A
TF-like sequence located between -2764 bp and -2753 bp in the upstream
regulatory region for the human IL-I beta gene. DNaseI protection, ge
l mobility shift analysis, and cotransfection studies were performed t
o investigate the binding and functional properties of E4BP4 using IL-
1 beta promoter sequences. By DNaseI footprinting, a protection patter
n was generated over the CRE/ATF-like site and the flanking sequences
by bacterially produced E4BP4. Competition experiment by,eel shift ass
ay indicated that E4BP4 bound specifically to CRE/ATF-like site, not N
F kappa B-like site. In cotransfection studies, E4BP4 repressed promot
er activity and this repression was mediated through the CRE/ATF-like
site. Mutational analysis of E4BP4 suggested that the DNA binding as w
ell as repression activities required leucine heptad repeat domain. An
alysis of E4BP4 produced in Escherichia coli and Sf9 cells infected wi
th recombinant baculovirus indicated that baculovirus produced protein
showed enhanced binding to the CRE/ATF-like site compared to the E. c
oli-produced protein. Analysis of posttranslational modifications indi
cated that E4BP4 produced in Sf9 cells was phosphorylated and this pho
sphorylation was important for the DNA binding activity of E4BP4.