The sequence of the chicken interferon-gamma (ifn-gamma) gene was dete
rmined, one of the first non-mammalian cytokine gene structures to be
elucidated. Initial genomic clones were amplified from chicken genomic
DNA and were used to isolate a cosmid clone covering the entire gene
for sequencing. The exon:intron structure of chicken ifn-gamma is very
similar to those of its mammalian homologues, with the exception of t
he third intron, which is markedly shorter in the chicken. The first e
xon contains both 5' UTR and signal sequence and the first 22 aa of th
e mature protein. The remainder of the coding region lies in exons 2-4
. Exon 4 also encodes the stop codon and the 3' UTR, including two pos
sible polyadenylation signals. A number of potential regulatory sequen
ces similar to those found in mammals have been identified, in the pro
moter, in each intron and in the 3' UTR. In the promoter, these includ
e the TATAATA- and CCAT-boxes, a consensus GATA motif in the reverse o
rientation and a potential NF-kappa B binding site. Other regulatory e
lements identified in the promoters of mammalian ifn-gamma genes are a
bsent. Internal to the gene structure, regulatory sequences identified
include elements found in the DNase I hypersensitivity region of the
first intron of the human ifn-gamma gene and several potential NF-kapp
a B binding sites. The 3' UTR contains an AT-rich sequence, including
nine repeats of the 'instability' motif ATTTA. As in mammals, chicken
ifn-gamma is a single copy gene. The gene is highly conserved, with no
polymorphisms yet identified using either RFLP or SSCP in the coding
region. However, promoter sequence polymorphisms between different inb
red lines of chickens have been identified, with possible links to dis
ease resistance. (C) 1998 Elsevier Science B.V.