The hepatotrophic factor designated augmenter of liver regeneration (ALR) is thought to be one of the factors responsible for the extraordinary regenerative capacity of mammalian liver. It has also been called hepatic regenerative stimulation substance (HSS). The gene resides on chromosome 16 in the interval containing the locus for polycystic kidney disease (PKD1). The putative gene product is 42% similar to the scERV1 protein of yeast. The yeast scERV1 gene had been found to be essential for oxidative phosphorylation, the maintenance of mitochondrial genomes, and the cell division cycle. The human gene is both the structural and functional homolog of the yeast scERV1 gene.