3-Hydroxy-3-methylglutaryl coenzyme A synthase-1 of Blattella germanica has structural and functional features of an active retrogene

Blattella germanica has two cytosolic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase genes, HMG-CoA synthase-l and -2. HMG-CoA synthase-1 ge ne shows several features of processed genes (retroposons): it contains no introns but has a short direct-repeat sequence (ATTATTATT) at both ends. An atypical feature is the presence at both ends of the gene of short inverse repeats flanked by direct repeats. There is neither a TATA box nor a CAAT box in the 5' region. Comparative analysis with other species suggests that the HMG-CoA synthase-1 gene derives from HMG-CoA synthase-2. Cultured embr yonic B. germanica UM-BGE-1 cells express HMG-CoA synthase-1 but not HMG-Co A synthase-2, suggesting that the intron-less gene is functional. In additi on, it can complement MEV-1 cell line, which is auxotrophic for mevalonate. We show that compactin and mevalonate do not significantly affect the mRNA levels of HMG-CoA synthase-1 in UM-BGE-1 cells. Compactin induces a 6.7-fo ld increase in HMG-CoA reductase activity, which is restored to normal leve ls by mevalonate. HMG-CoA synthase activity is not modified by either of th ese effecters, suggesting that the mevalonate pathway in this insect cell l ine is regulated by post-transcriptional mechanisms affecting HMG-CoA reduc tase but not HMG-CoA synthase. (C) 2001 Elsevier Science Ltd. All rights re served.