J. Biol. Chem., Vol. 261, Issue 17, 7588-7591, 06, 1986
The 5' flanking region of the ornithine transcarbamylase gene contains DNA sequences regulating tissue-specific expression
G Veres, WJ Craigen and CT Caskey
Ornithine transcarbamylase (OTCase) is a mitochondrial matrix enzyme that
catalyzes the 2nd step in the mammalian urea cycle. The gene encoding
OTCase is located on the X chromosome and expression of OTCase is limited
almost exclusively to hepatocytes. We have characterized a lambda phage
recombinant, isolated from a mouse genomic library, that spans the first
two exons of the mouse OTCase gene. Nuclease S1 mapping and primer
extension analysis of this clone allowed us to determine that the
transcription start site is 136 base pairs (bp) upstream from the
translation initiation codon. Two TATA-like sequences were found 25 and 153
bp from the transcription initiation point. An 800-bp fragment containing
the 5' flanking region of the OTCase gene was fused upstream to the coding
sequence of the chloramphenicol acetyltransferase gene to assay promoter
activity. This plasmid was introduced into mouse fibroblast NIH 3T3 cells
and human hepatoma Hep G2 cells by the calcium phosphate co-precipitation
method. After DNA transfection chloramphenicol acetyltransferase activity
was observed only in Hep G2 cells. We conclude that this 800-bp fragment
contains sufficient information to control OTCase gene expression in a
tissue-specific manner, probably by interacting with trans-acting factor(s)
which are not present in the other cell line.