Alternative splicing of the human diacylglycerol kinase ζ gene in muscle

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Abstract
Diacylglycerol can function as a second messenger, and one mechanism for the attenuation of this signal is its conversion to phosphatidic acid, which is catalyzed by diacylglycerol kinase (DGK). We screened a cDNA library from human skeletal muscle and isolated two DGKζ cDNAs that differed from the 3.5-kb clone originally identified in endothelial cells. One transcript, which was 3.4 kb long, was shown to be nonfunctional; it had a 77-bp deletion that included the translation initiation site. The other was 4.1 kb long with a unique 5′ sequence of 853 bp. We also isolated a genomic clone of DGKζ and determined its organization and location; it contains 32 exons, spans approximately 50 kb of genomic sequence, and maps to chromosome 11p11.2. The protein encoded by the 4.1-kb transcript contains two cysteine-rich regions, a catalytic domain, and ankyrin repeats like the endothelial form of DGKζ, as well as a unique N-terminal domain. The coding sequence was shown to be derived from alternative splicing of the DGKζ gene. In cells transfected with the 4.1-kb clone, we detected a 130-kDa protein with an antibody to DGKζ and demonstrated that it was localized predominantly in the nucleus. We conclude that alternative splicing generates tissue-specific variants of DGKζ that share some properties but may have unique ones as well.