Manabu Shimonishi

Molecular cloning and expression of human hepatocyte growth factor

HEPATOCYTE growth factor (HGF) is the most potent mitogen for mature parenchyma! hepatocytes in primary culture, and seems to be a hepatotrophic factor that acts as a trigger for liver regeneration after partial hepatectomy and liver injury. The partial purification and characterization of HGF have been reported1–4. We have demonstrated that pure HGF from rat platelets is a new growth factor5, 6 effective at concentrations as low as 1 ng mP−1.The effects of HGF and epidermal growth factor (EGF) are additive. The activity of HGF is not species-specific, although it does not stimulate growth in Swiss 3T3 fibroblasts5. HGF has a relative molecular mass (Mr) of 82,000 and is a heterodimer composed of a large a-subunit of Mr 69,000 and a small β -subunit of Mr34,000 (ref. 6). Here we report the amino-acid sequence of human HGF determined by complementary DNA cloning and the expression of biologically active human HGF from COS-1 cells transfected with cloned cDNA. The nucleotide sequence of the human HGF cDNA reveals that both α- andβ-chains are contained in a single open reading frame coding for a pre-pro precursor protein of 728 amino acids.

Analysis of the structure and expression of the Augmenter of Liver Regeneration (ALR) gene

BackgroundThe gene encoding the hepatotrophic factor Augmenter of Liver Regeneration (ALR) has recently been cloned in the rat. The availability of the mouse form of ALR would allow the analysis of the role of this factor in the physiology of liver and other organs, while the identification of the human homolog would allow the transfer of the great wealth of information that has been generated in animal models to clinically oriented pilot trials, and eventually the therapeutic application of this information.Materials and MethodsStandard molecular biology approaches have been used to determine the genomic structure of the ALR gene in the mouse, and to characterize the ALR transcript and its protein product. The human ALR cDNA was also isolated and the amino acid sequence of the human gene product deduced. The mapping of mouse and human ALR genes on mouse and human chromosomes was then completed.ResultsThe protein coding portion of the mouse ALR gene is comprised of three exons, the first containing the 5′ untranslated sequence and the initial 18 bases after the ATG translation initiation codon, the second exon encompasses 198 bases, and the third exon contains the remaining portion of the protein coding sequence. Rat, mouse, and human ALR genes (and protein products) were found to be highly conserved and preferentially expressed in the testis and in the liver. The ALR gene maps to the mouse chromosome 17, in a region syntenic with human chromosome 16, where the T/t region has also been mapped.ConclusionsALR appears to be a protein with important physiologic properties, not exclusively limited to liver regeneration, with roles that are involved in the synthesis or stability of the nuclear and mitochondrial transcripts that are present in actively regenerating cells, particularly the germ cells of the testes.