Using a small cell lung cancer (SCLC) cDNA library, we obtained clones for the creatine kinase-B (CK-B) gene and determined the nucleotide sequence for the protein coding and 3' untranslated region (3' UT). The human translated protein spans 381 residues and the amino acid homology with rabbit CK-B is >98%. We have demonstrated that a nucleic acid probe encompassing the protein coding region will also hydridize to CK-M sequences while a probe derived from the 3' UT region is CK-B specific. When a B-isoenzyme specific sequence is hybridized to Eco RI cut genomic DNA, two independent restriction fragment polymorphisms are detected. We have subsequently localized these two CK-B homologous sequences to chromosomes 14q32 and 16. Finally, we show that increased levels of CK-B seen in SCLC are not accompanied by gene amplification or rearrangement, but reflect a greatly enhanced level of CK-B specific mRNA that is not seen in non-SCLC lines thus far examined.
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