1: Mol Cell Endocrinol. 1996 Mar 25;117(2):167-73. 

The same sequence mediates activation of the human urokinase promoter by cAMP in
mouse Sertoli cells and by SV40 large T antigen in COS cells.

Grimaldi P, Geremia R, Albanesi C, Rossi P.

Dipartimento di Sanita Pubblica e Biologia Cellulare, Universita di Roma Tor
Vergata, Italy.

Cell-specific activation by follicle-stimulating hormone and its intracellular
mediator, cAMP, of the human urokinase promoter in mouse Sertoli cells requires
overlapping purine-rich and GC-rich sequences between -54 and -42 from the
transcriptional start site. We have previously shown that binding of
unidentified nuclear factors to these sequences is induced by cAMP stimulation,
and that sequences from the enhancerless SV40 replication origin can interfere
with the binding, whereas consensus Sp1 binding sites are ineffective. We now
show that sequences within the SV40 origin able to compete for the formation of
cAMP-induced DNA-protein complexes in Sertoli cell nuclear extracts are binding
sites for the SV40 large T antigen. Large T antigen expressed in COS cells binds
the cAMP-responsive sequences of the human urokinase gene and transactivates the
proximal promoter, thus mimicking the effect of nuclear factors induced by cAMP
in Sertoli cells. We show that Egr-1 is one of the factors present in
cAMP-induced DNA-protein complexes formed between the human urokinase promoter
and Sertoli cell nuclear extracts. However, Egr-1 levels are similar in
unstimulated and cAMP-treated Sertoli cells, suggesting that this factor
interacts with a different GC-box binding factor, that we have previously shown
to be strongly induced by cAMP treatment of Sertoli cells. We propose that SV40
large T antigen in COS cells can mimick the action of heterodimers formed in
cAMP stimulated Sertoli cells between Egr-1 and a cell specific cAMP-induced
GC-box binding factor.

PMID: 8737376 [PubMed - indexed for MEDLINE]


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