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Mol. Cell. Biol., Apr 1995, 2080-2089, Vol 15, No. 4
KS LaForge, EM Unterwald and MJ Kreek
We isolated the guinea pig preproenkephalin gene from a genomic library by
hybridization to a rat cDNA probe. The entire nucleotide sequence of the
gene was determined. Genomic Southern blot hybridization demonstrated that
the gene exists in a single copy within the genome. On the basis of RNase
protection transcript mapping and homology comparisons with known
preproenkephalin sequences from other species and assuming a poly(A) tail
length of 100 residues, we predicted an mRNA transcript of approximately
1,400 nucleotides encoded by three exons. Northern (RNA) blot analysis of
total RNA from several brain regions showed high levels of preproenkephalin
mRNA in the caudate putamen, nucleus accumbens, and hypothalamus, with
detectable levels in the amygdala, ventral tegmental area, and central gray
and also in the pituitary. Unexpectedly, in several brain regions, the mRNA
appeared not only in the 1,400-nucleotide length but also in a shorter
length of approximately 1,130 bases. Significant amounts of the shorter
mRNA were found in the caudate putamen, nucleus accumbens, and amygdala.
The longer, but not the shorter, transcripts from the caudate putamen were
found to be polyadenylated, but the difference in size was not due solely
to the presence of poly(A) tails. Northern gel analysis of total RNA from
the caudate putamen with probes from each exon, together with RNase
protection mapping of the 3' end of the mRNA demonstrated that the
1,400-base preproenkephalin mRNA transcripts are cleaved in a site-
specific manner in some brain regions, yielding a 1,130-base transcript and
a 165-base polyadenylated fragment derived from the terminal end of the 3'
untranslated region of the mRNA. This cleavage may serve as a preliminary
step in RNA degradation and provide a mechanism for control of
preproenkephalin mRNA abundance through selective degradation.
Copyright © 1995, American Society for Microbiology
Structure and expression of the guinea pig preproenkephalin gene: site- specific cleavage in the 3' untranslated region yields truncated mRNA transcripts in specific brain regions
Rockefeller University, New York, New York 10021.
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