Isolation and characterization of a complementary DNA (PD-1) differentially expressed by human pancreatic ductal cell...

A complementary DNA (cDNA) library from a cloned subline (CD-11) of a well differentiated human pancreatic tumor cell line, HPAF, was subjected to differential screening using single stranded cDNA probes synthesized from mRNA of the well differentiated cell clone CD-11 and a poorly differentiated pancreatic tumor cell line, Panc 1. A cDNA clone (PD-1) was identified which had an insert of 626 base pairs (bp). PD-1 cDNA hybridized to a transcript of about 650 bp on Northern blot analysis, suggesting that the cDNA was close to full length. Densitometric analysis of Northern blots showed that a well differentiated pancreatic tumor line had a 5-fold higher PD-1 expression as compared to the poorly differentiated line, Panc 1. Nucleotide sequence analysis of the PD-1 cDNA and its deduced amino acid sequence showed an open reading frame of 399 bp. In addition to the open reading frame, the sequence had a 5' untranslated region of 61 bp and a 3' untranslated tail of 147 bp. The nucleotide sequence did not show any significant homology to any other sequence in the GENBANK or EMBL databases; however, the translated protein showed 35% homology to bacterial ribosomal proteins over 112 amino acids. Sequence analysis of the PD-1 cDNA and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of its in vitro transcription/translation product suggest that this gene encoded a protein of 16,000 daltons.(ABSTRACT TRUNCATED AT 250 WORDS)