Z. Xu et Brg. Williams, GENOMIC FEATURES OF HUMAN PKR - ALTERNATIVE SPLICING AND A POLYMORPHIC CGG REPEAT IN THE 5'-UNTRANSLATED REGION, Journal of interferon & cytokine research, 18(8), 1998, pp. 609-616
The double-stranded RNA-dependent protein kinase (PKR) is a serine/thr
eonine kinase that plays an important role in the antiviral activities
of interferon (IFN). To determine the organization and regulation of
the PKR locus, lambda phage and bacterial artificial chromosome (BAC)
clones containing the human PKR gene were isolated. Characterization o
f these clones revealed that PKR has 17 exons and 16 introns dispersed
in a genomic region of 50 kb, Sequence analysis of the PKR 5'-flankin
g region identified a canonical IFN-stimulated response element (ISRE)
, GAAAACGAAACT. Transient transfection of PKR promoter constructs link
ed to a luciferase reporter gene into human T98G cells indicated that
this 5'-flanking region is capable of functioning as a basal promoter
that is also inducible by IFN-alpha and IFN-beta but not IFN-gamma. In
terestingly, the PKR gene contains a polymorphic CGG trinucleotide rep
eat in exon 1, In addition, four PKR alleles, varying in repeat number
from 7 to 10, were detected in 30 individual chromosomes. The PKR gen
e undergoes alternative splicing of exon 2, which gives rise to two fo
rms of 5'-untranslated exons of different length. Although the human a
nd murine PKR proteins have high homology, comparison of their gene st
ructures reveals divergence in 5'-flanking regions, suggesting distinc
t regulation at the genomic level.