ALTERNATIVE SPLICING OF THE HUMAN DIACYLGLYCEROL-KINASE-ZETA GENE IN MUSCLE

Diacylglycerol can function as a second messenger, and one mechanism f or the attenuation of this signal is its conversion to phosphatidic ac id, which is catalyzed by diacylglycerol kinase (DGK), We screened a c DNA library from human skeletal muscle and isolated two DGK zeta cDNAs that differed from the 3.5-kb clone originally identified in endothel ial cells, One transcript, which was 3.4 kb long, was shown to be nonf unctional; it had a 77-bp deletion that included the translation initi ation site. The other was 4.1 kb long with a unique 5' sequence of 853 bp, We also isolated a genomic clone of DGK zeta and determined its o rganization and location; it contains 32 exons, spans approximately 50 kb of genomic sequence, and maps to chromosome 11p11.2. The protein e ncoded by the 4.1-kb transcript contains two cysteine-rich regions, a catalytic domain, and ankyrin repeats like the endothelial form of DGK zeta, as well as a unique N-terminal domain, The coding sequence was shown to be derived from alternative splicing of the DGK zeta gene. In cells transfected with the 4.1-kb clone, we detected a 130-kDa protei n with an antibody to DGK zeta and demonstrated that it was localized predominantly in the nucleus. We conclude that alternative splicing ge nerates tissue-specific variants of DGK zeta that share some propertie s but may have unique ones as well.