[Isolation and characterization of a novel transcript of hepatopoietin]

A novel transcript of human HPO (HPO-205) encoding a 205 amino acid ORF corresponding to a translated product of 23 kD different from the previous HPO that lacks the N-terminal 80 amino acids, was isolated from human fetal liver cDNA library by 5'RACE methods. The dose-dependent stimulation of DNA synthesis of HepG2 hepatoma cells by HPO-205 demonstrated its similar biological activity with HPO in vitro. The level of MAPK (mitogen-activated protein kinase)phosphorylation was further examined by Western blot analysis and the result revealed that HPO-205 protein might have stronger activity on stimulating hepatic cell proliferation than that of HPO. The similar result was observed by FACS technique. Therefore, our results suggest that the HPO-205 has activity to stimulate proliferation of liver derived cells, and this activity may be stronger than HPO.