A. Aguanno et al., TISSUE-SPECIFIC EXPRESSION OF THE NONNEURONAL PROMOTER OF THE AROMATIC L-AMINO-ACID DECARBOXYLASE GENE IS REGULATED BY HEPATOCYTE-NUCLEAR-FACTOR-1, The Journal of biological chemistry, 271(8), 1996, pp. 4528-4538
The rat aromatic L-amino acid decarboxylase (AADC) gene contains alter
native promoters which direct expression of neuronal and nonneuronal m
RNAs that differ only in their 5'-untranslated regions (UTRs). We have
analyzed the expression of the nonneuronal promoter of the rat AADC g
ene in the kidney epithelial cell line LLC-PK1 and in cells which do n
ot express the nonneuronal form of AADC by transient transfection. The
se studies revealed that the first 1.1 kilobases of the nonneuronal pr
omoter, including the nonneuronal-specific 5'-UTR (Exon 1), contains s
ufficient information to direct tissue-specific expression. Serial del
etions of this promoter localized the cis-active element to a region b
etween -52 and -28 base pairs upstream of the nonneuronal transcriptio
n start site. An APT-rich sequence, within this region which we have t
ermed KL-1, was found to bind a kidney and liver-specific factor by DN
ase footprint analysis and was capable of directing tissue-specific ex
pression from a heterologous promoter. Moreover, when the KL-1 sequenc
e was mutated in the context of the entire promoter sequence, all tran
scriptional activity was abolished. DNA sequence comparison revealed t
hat the KL-1 fragment is highly homologous to the binding site for hep
atocyte nuclear factor-1 (HNF-1). Mobility shift studies utilizing an
antibody to HNF-1 demonstrated binding of HNF-1 to the KL-1 fragment a
nd cotransfection of HNF-1 cDNA into cells which do not express the no
nneuronal form of AADC resulted in activation of transfected AADC nonn
euronal promoter constructs. These results strongly suggest that the t
ranscription factor which regulates the tissue-specific expression of
the nonneuronal form of AADC mRNA is HNF-1.