Identification and characterization of a novel isoform of hepatopoietin.
OBJECTIVE
To isolate a novel isoform of human HPO (HPO-205) from human fetal liver Marathon-ready cDNA and characterize its primary biological function.


METHODS
5'-RACE (rapid amplification of cDNA 5' ends) was used to isolate a novel isoform of hHPO in this paper. The constructed pcDNA(HPO-205), pcDNA(HPO) and pcDNA eukaryotic expression vectors were respectively transfected by lipofectamine method and the stimulation of DNA synthesis was observed by (3)H-TdR incorporation assay. Proteins extracted from different cells were analyzed by Western blot.


RESULTS
A novel isoform of hHPO (HPO-205) encoding a 205 amino acid ORF corresponding to a translated production of 23 kDa was isolated and distinguished from the previous HPO that lacked the N-terminal 80 amino acids. 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 by Western blot analysis revealed that HPO-205 might have the stronger activity of stimulating hepatic cell proliferation than that of HPO.


CONCLUSIONS
A novel isoform of hHPO (HPO-205) was isolated from hepatic-derived cells. The comparison of HPO-205 and HPO will lead to a new insight into the structure and function of hHPO, and provide the new way of thinking to deeply elucidate the biological roles of HPO/ALR.
Lu
Jun
J
Institute of infectious Disease, First Affiliated Hospital, Medical School, Zhejiang University, Hangzhou 310003, China.
Xu
Wang-Xiang
WX
Zhan
Yi-Qun
YQ
Cui
Xiao-Lin
XL
Cai
Wei-Min
WM
He
Fu-Chu
FC
Yang
Xiao-Ming
XM
D000595:Amino Acid Sequence; D002455:Cell Division; D002458:Cell Fractionation; D004789:Enzyme Activation; D017228:Hepatocyte Growth Factor / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification* / Q000494:pharmacology; D006801:Humans; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D020033:Protein Isoforms; D016415:Sequence Alignment; D014407:Tumor Cells, Cultured
D020033:Protein Isoforms; D017228:Hepatocyte Growth Factor; D020928:Mitogen-Activated Protein Kinases