Abstract
Prostaglandin E2 (PGE2) plays an important role in protection of the gastric mucosa against various damaging agents and growth‐inhibitory activity on tumor cells. However, the precise regulation mechanism of PGE2 in gastric cancer cells is still unclear. In this study, we isolated a gene, which is regulated by PGE2 in SNU‐1, human gastric adenocarcinoma cells, using differential display RT‐PCR (DD RT‐PCR) and characterized the function of the gene induced by PGE2. The full‐length cDNA of the gene was cloned by the rapid amplification of cDNA ends method. The 1659 base pair cDNA consists of a 30‐nt 5′‐noncoding region, an 891‐nt open reading frame and a 738‐nt 3′noncoding region that includes a poly (A) signal. As a result of protein motif search, we found that it has a conserved thioredoxin‐active site, Cys‐Gly‐Pro‐Cys and a Myb‐DNA binding domain repeat signature. Thus, we designated this gene product as thioredoxin‐related protein‐1, TRP‐1. TRP‐1 was expressed in a lower extent in renal, gastric and colon cancer tissues and is translated into 33 kDa protein in nuclear and cytoplasmic fractions. TRP‐1 has a thioredoxin activity, which was detected using the insulin disulfide reduction assay. Another potential role of TRP‐1 is repression of B‐Myb activity through direct binding to B‐Myb, a transcriptional factor induced at G1–S transition. Finally, TRP‐1 overexpression inhibits mammalian cell proliferation and specifically predispose to G0/G1 phase arrest. In conclusion, these results imply that TRP‐1 is a mammalian thioredoxin and plays as a transcriptional repressor through direct binding to the transcription factor B‐Myb. © 2005 Wiley‐Liss, Inc.
