Regulation of albumin mRNA in H4 rat hepatoma cells by the availability of essential amino acids.

Deprivation of cultured H4 rat hepatoma cells for an essential amino acid (leucine, methionine, tryptophan or phenylalanine) under conditions in which the cells remain highly viable leads to a decrease in cytoplasmic albumin mRNA. The magnitude of this decrease is greatest in tryptophan-deprived and phenylalanine-deprived cells. In the tryptophan-deprived cells there is approximately a 15-17-fold decrease in albumin mRNA relative to total cytoplasmic RNA, and a 7-8-fold specific decrease in albumin mRNA relative to alpha-tubulin mRNA. Deprivation of the H4 cells for leucine or tryptophan causes approximately a 40-45% decrease in albumin gene transcription; however, this effect does not account for the 15-17-fold decrease in albumin mRNA abundancy caused by tryptophan limitation, or the greater effect of tryptophan limitation as compared to leucine limitation on albumin mRNA. Therefore, the decrease in albumin mRNA caused by tryptophan limitation is caused primarily by a post-transcriptional regulatory mechanism.