Hp. Shi et Ct. Teng, CHARACTERIZATION OF A MITOGEN-RESPONSE UNIT IN THE MOUSE LACTOFERRIN GENE PROMOTER, The Journal of biological chemistry, 269(17), 1994, pp. 12973-12980
Lactoferrin is present in a variety of tissues and biological fluids;
however, the amount differs significantly due to differential expressi
ons. We have previously demonstrated that the mouse lactoferrin gene i
s regulated by estrogen through an estrogen-response DNA element locat
ed at -349, upstream from the transcription start site (+1). In this r
eport, we characterized by deletion and mutation analyses a cluster of
mitogen-response elements located between -80 and -40 of the mouse la
ctoferrin promoter. We demonstrated that the chimeric chloramphenicol
acetyltransferase reporter constructs (the -103 to +1 sequence of the
mouse lactoferrin gene) containing the mitogen-response unit of the la
ctoferrin gene were stimulated by cAMP, forskolin, 12-O-tetradecanoylp
horbol-13-acetate, and epidermal growth factor/recombinant transformin
g growth factor-alpha (EGF/TGF-alpha) in a time- and dose-dependent ma
nner. The sequence at position -52 to -40 (mLF-CRE) of the gene confer
red transcriptional activation in the presence of forskolin, cyclic AM
P, and 12-O-tetradecanoylphorbol-13-acetate in transiently transfected
human endometrium carcinoma RL95-2 cells, whereas the region at -80 t
o -60 responded to EGF/TGF-alpha stimulation. Overexpression of the ca
talytic unit of protein kinase C or protein kinase A in the RL95-2 cel
ls elevated the chloramphenicol acetyltransferase activity of the repo
rter construct 5-6-fold. The mobility shift assay suggested that AP1 a
nd CREB or related proteins participated in complex formation with the
mLF-CRE, whereas different proteins bound to the EGF/TGF-alpha-respon
se element.