Isolation and characterization of the bovine corticotropin/beta-lipotropin precursor gene.

Abstract

The entire bovine corticotropin/beta-lipotropin precursor gene has been isolated as a set of overlapping genomic DNA fragments which extend over a length of approximately 17000 base pairs. Restriction mapping of the cloned DNA fragments and nucleotide sequence analysis of the whole mRNA-coding segments and their surrounding regions have established that the corticotropin/beta-lipotropin precursor gene is approximately 7300-base-pairs long and contains two intervening sequences; one with an approximate length of 4000 base pairs is located within the segment encoding the 5'-untranslated region of the mRNA, and the other with an approximate length of 220 base pairs interrupts the protein-coding sequence near the signal peptide region. Sequence analysis of more than 200 base pairs preceding the proximal end of the corticotropin/beta-lipotropin precursor gene has revealed a 'Hogness box' and a variant of the model sequence d(G-G-TC-C-A-A-T-C-T) as well as palindrome structures as observed in other eukaryotic genes. Furthermore, some sequence similarities in the 5'-flanking region are found between the corticotropin/beta-lipotropin precursor gene and the mouse alpha-globin and beta-globin genes, all of which are negatively regulated by glucocorticoids. At least four homologous repetitive sequences are distributed at 3000-5000-base-pair distances in the corticotropin/beta-lipotropin precursor gene region; two such sequences are located in the 5'-flanking region, and one within each intervening sequence. Blot hybridization analysis of bovine pituitary nuclear RNA has indicated that the entire corticotropin/beta-lipotropin precursor gene is transcribed into a primary hnRNA product, which is then spliced to form the mature mRNA.