A novel nk-2-related transcription factor associated with human fetal liver and hepatocellular carcinoma

J Biol Chem. 1998 Jan 30;273(5):2917-25. doi: 10.1074/jbc.273.5.2917.

Abstract

A novel cDNA was partially isolated from a HepG2 cell expression library by screening with the promoter-linked coupling element (PCE), a site from the alpha-fetoprotein (AFP) gene promoter. The remainder of the cDNA was cloned from fetal liver RNA using random amplification of cDNA ends. The cDNA encodes a 239-amino acid peptide with domains closely related to the Drosophila factor nk-2. The new factor is the eighth vertebrate factor related to nk-2, hence nkx-2.8. Northern blot and reverse transcriptase polymerase chain reaction analysis demonstrated mRNA in HepG2, two other AFP-expressing human cell lines, and human fetal liver. Transcripts were not detected in adult liver. Cell-free translation produced DNA binding activity that gel shifted a PCE oligonucleotide. Cotransfection of nkx-2.8 expression and PCE reporter plasmids into HeLa cells demonstrated transcriptional activation; NH2-terminal deletion eliminated this activity. Cotransfection into AFP-producing hepatocytic cells repressed AFP reporter expression, suggesting that endogenous activity was already present in these cells. In contrast, cotransfection into an AFP-negative hepatocytic line produced moderate activation of the AFP gene. The cardiac developmental factor nkx-2.5 could substitute for nkx-2.8 in all transfection assays, whereas another related factor, thyroid transcription factor 1, showed a more limited range of substitution. Although the studies have yet to establish definitively that nkx-2.8 is the AFP gene regulator PCF, the two factors share a common DNA binding site, gel shift behavior, migration on SDS-acrylamide gels, and cellular distribution. Moreover, the nk-2-related genes are developmental regulators, and nkx-2.8 is the first such factor associated with liver development.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Binding Sites
  • Carcinoma, Embryonal
  • Carcinoma, Hepatocellular
  • Cloning, Molecular
  • Gene Expression Regulation, Developmental*
  • Humans
  • Liver / growth & development
  • Liver Neoplasms
  • Molecular Sequence Data
  • Neoplasm Proteins / genetics*
  • Promoter Regions, Genetic
  • Sequence Homology, Amino Acid
  • Transcription Factors / metabolism
  • alpha-Fetoproteins / biosynthesis*
  • alpha-Fetoproteins / genetics

Substances

  • Neoplasm Proteins
  • Transcription Factors
  • alpha-Fetoproteins

Associated data

  • GENBANK/AF000295
  • GENBANK/AF000296
  • GENBANK/AF000297