Expression and cDNA cloning of human HMGI-C phosphoprotein.

The HMGI family contains three members: I, Y and I-C. HMGI and HMGY are alternative splicings of the same gene and are essential transcription factors at several genetic loci. HMGI-C is transcribed from a different gene and is observed only in highly transformed cells. This work shows that human I-C is present in a more restricted range of cell types than I/Y and is absent from hemopoietic cells, as noted for mouse I-C. However, high expression in a human hepatoma line allowed the cloning of the cDNA and 812 bp of 5'-untranslated, 330 bp of coding and 58 bp of 3'-untranslated DNA were sequenced. The open reading frame showed 4 amino acid substitutions and one additional amino acid when compared to mouse I-C, none of them in the basic DNA binding motifs.