Human augmenter of liver regeneration: Molecular cloning, biological activity and roles in liver regeneration

The complete amino acid sequence of human augmenter of liver regeneration (hALR) was reported by deduction from nucleotide sequence of its complementary DNA. The cDNA for hALR was isolated by screening a human fetal liver cDNA library and the sequencing of this insert revealed an open reading frame encoding a protein with 125aa and highly homologous (87%) with rat ALR encoding sequence. The recombinant hALR expressed from its cDNA in transient expression experiments in cos-7 cells could stimulate DNA synthesis of HTC hepatoma cell in the dose-dependent and heat-resistant way. Northern blot analysis with rat ALR cDNA as probe confirmed that ALR mRNA was expressed in the normal rat liver at low level and that dramatically increased in the regenerating liver after partial hepatectomied rat. This size of hALR mRNA is 1.4 kb long and expressed in human fetal liver, kidney and testis. These findings indicated that liver itself may be the resource of ALR and suggested that ALR seems to be an important paracrined regulator of liver regeneration.