Complex molecular structure of the gene coding for rat ceruloplasmin.

The distribution of ceruloplasmin-coding sequences among the fragments of rat nuclear DNA obtained after the complete digestion with seven restriction endonucleases (EcoRI, BamHI, BspI, HindIII, KpnI, BglII and XhoI) was studied using highly specific cDNA probes. Although only a single copy of this gene per rat haploid genome was detected in DNA-cDNA hybridization in solution, the number of restriction fragments carrying the sequences of ceruloplasmin (CP) gene varied from two to five, depending upon the enzyme used, and their total length was several times higher than the minimal length of CP-coding gene, as deduced from the size of mRNA (2.3 Md for double-stranded DNA). The partial double stranded DNA transcript of ceruloplasmin mRNA coding for about 70% of its length (from 3'-end) does not contain recognition sites for some restriction endonucleases generating multiple fragments of CP gene in cellular DNA. These data are consistent with a split pattern of CP gene which seems to consist of several exons and introns. The partial protection from S1 nuclease of discrete fragments of full-length cDNA after annealing with high molecular weight nuclear RNA is consistent with this assumption and seems to be an indication that exons and introns are joined into a functional unit coding for high mol wt. CP pre-mRNA.