Molecular cloning of a cDNA sequence complementary to porphobilinogen deaminase mRNA from rat.

A cDNA clone containing sequences complementary to the mRNA coding for anemic rat spleen porphobilinogen deaminase (EC 4.3.1.8) has been isolated. A cDNA library was prepared from partially purified mRNA (1% purity). This library was then screened by colony hybridization, using a cDNA probe derived from porphobilinogen deaminase mRNA further enriched (10-20% purity) by gel electrophoresis in the presence of methylmercury hydroxide. Colonies hybridizing with the probe were analyzed by hybrid-selected translation using anemic rat spleen mRNA. Four recombinant plasmids containing porphobilinogen deaminase cDNA sequences were identified by specific immunoprecipitation of the translational product from hybrid-selected mRNA. Porphobilinogen deaminase mRNA was shown to contain 1800 bases by blot hybridization analysis. The cloned cDNA sequence consists of 1500 bases. Hybridization analysis of poly(A)+ RNA from uninduced and induced mouse erythroleukemic cells indicated that induction to erythroid differentiation by dimethyl sulfoxide results in a 10-fold increase of porphobilinogen deaminase mRNA. The rat cDNA clones hybridize to the corresponding sequences encoding human porphobilinogen deaminase. This property will be useful for isolation of human gene(s) and further characterization of the molecular lesion(s) responsible for acute intermittent porphyria.