CLONING AND EXPRESSION ANALYSIS OF A CDNA-ENCODING FUMARYLACETOACETATE HYDROLASE - POSTTRANSCRIPTIONAL MODULATION IN RAT-LIVER AND KIDNEY

Fumarylacetoacetate hydrolase (FAH) is an enzyme which is deficient in human hereditary tyrosinemia type 1. We have cloned and sequenced a rat liver cDNA encoding FAH. The identity of the clone was ascertained by hybrid-selection experiments and deduced amino acid (aa) sequence homologies with sequenced oligopeptide fragments of the purified rat liver protein. The cDNA codes for a 419-aa protein of 45 946 daltons. We used this cDNA as a probe in conjunction with a specific anti-rat FAH antibody to study the expression pattern of the FAH gene in rat liver and kidney. Northern blot analysis indicates that the kidney contains slightly more FAH mRNA than the liver. Western blotting shows, however, that the liver contains about twice as much FAH protein as the kidney. Primer extension experiments suggest that there are no differences in the 5'-untranslated (UT) ends of the FAH mRNA of both tissues. We conclude that synthesis of the FAH protein is in part regulated at the post-transcriptional level in rat liver and kidney, and that this regulation does not appear to be mediated by the 5'-UT sequence of the FAH mRNA.