| Summary: | 博士 === 國立臺灣大學 === 臨床醫學研究所 === 82 === We had taken the strategy of differential screening of cDNA
library between two human colorectal cancer cell lines with
different differentiation status, to search for possible useful
cancer markers. we has cloned a few cDNA clones which are
overexpressed in colorectal cancer tissues. One of these clones
was found to be the 67 kDa human laminin receptor. Another
clone had been found to be the ubiquitin ribosomal protein 27a
gene. We had screened a .lambda.gt10 cDNA library made from the
CX-1 human colon cancer cell line. A clone named J9 was picked
and was judged as a full length c DNA clone, it encodes a 295
amino acid protein with calculated molecular weight of about 33
kDa. Besides the unexpected small molecular weight of the
coding protein, J9 clone lacks a leader signal sequence at its
encoding protein''s N terminal, also it lacks a definite
transmembrane domain judged by hydropathy plot of its protein
sequence. We took the advantage of the full length character of
this J9 clone, tried to do in vitro expression of this gene to
solve above mentioned puzzles. Protein SDS-PAGE of the
translation product revealed molecular weight of about 45 kDa.
The biological meaning of the phenomenon of overexpression of
these two genes was tested with the model of stimulation of
quescient normal rat fibroblast cell line. The ubiquitin-S27a
ribosomal protein gene was shown to be a typical early growth
response gene, which is activated at early stage even in the
absence of protein synthesis. The 32/67 kDa laminin receptor
gene was found to be activated in early stage of growth
stimulation but the nuclear run on test failed to prove that
there is an early 32/67 kDa laminin receptor gene specific mRNA
transcription activity.
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