Lq. Cao et al., HUMAN GASTRIC ADENOCARCINOMA CATHEPSIN-B - ISOLATION AND SEQUENCING OF FULL-LENGTH CDNAS AND POLYMORPHISMS OF THE GENE, Gene, 139(2), 1994, pp. 163-169
Four full-length cDNA clones coding for preprocathepsin B were isolate
d from a human gastric adenocarcinoma cDNA library (AGS 1-6-30-1) and
analyzed for possible sequence modifications that might be linked to a
ltered intracellular trafficking and secretion of cathepsin B (CTSB) i
n malignant tumors. Comparison of AGS 1-6-30-1 cDNAs with human kidney
/hepatoma cDNAs revealed: (I) three potential hi-glycosylation sites i
nstead of two, (2) a nucleotide (nt) substitution in the coding region
for the propeptide from GTG to CTG which would result in a Val(26)-->
Leu change, (3) three silent nt replacements in the coding region for
the mature protein, (4) five single-nt differences in the 5'- and 3'-U
TR (untranslated regions), (5) heterogeneity in the 5'-UTR, and (6) a
10-bp insertion in the 3'-UTR. The 10-bp insertion in the 3'-UTR may a
lter the stability of CTSB mRNA transcripts and thereby the expression
of CTSB. These clones should be useful for expressing human tumor CTS
B and analyzing the function of this enzyme in malignant progression.
Two restriction-fragment length polymorphisms (RFLPs), EcoRI and TaqI,
were detected by Southern blot analysis of genomic DNA from 36 unrela
ted Caucasians. Inheritance and distribution of the EcoRI alleles (13.
0 and 11.0 kb) and the TaqI alleles (5.7 and 4.6 kb) indicated they we
re independent polymorphisms. In contrast to the EcoRI alleles of 13.0
and 11.0 kb observed in the population survey, genomic DNA from two A
GS gastric adenocarcinoma subclones revealed two EcoRI alleles of 13.0
and 7.8 kb. Whether the sequence modifications observed in the AGS 1-
6-30-1 CTSB cDNA clones are associated with its altered expression and
distribution of CTSB in tumors will require further investigation.