A NOVEL RNA SPECIES FROM THE TURTLE MITOCHONDRIAL GENOME - INDUCTION AND REGULATION OF TRANSCRIPTION AND PROCESSING UNDER ANOXIC AND FREEZING STRESSES

The present study identifies a previously cloned cDNA, pBTaR914, as ho mologous to the mitochondrial WANCY (tryptophan, alanine, asparagine, cysteine, and tyrosine) tRNA gene cluster. This cDNA clone has a 304-b p sequence and its homologue, pBTaR09, has a 158-bp sequence with a lo ng poly(A)(+) tail (more than 60 adenosines). RNA blotting analysis us ing pBTaR914 probe against the total RNA from the tissues of adult and hatchling turtles revealed five bands: 540, 1800, 2200, 3200, and 390 0 nucleotides (nt). The 540-nt transcript is considered to be an intac t mtRNA unit from a novel mtDNA gene designated WANCY(HP) that overlap s the WANCY tRNA gene cluster region. This transcript was highly induc ed by both anoxic and freezing stresses in turtle heart. The other tra nscripts are considered to be the processed intermediates of mtRNA tra nscripts with WANCY(HP) sequence. All these transcripts were different ially regulated by anoxia and freezing in different organs. The data s uggest that mtRNA processing is sensitive to regulation by external st resses, oxygen deprivation, and freezing. Furthermore, the fact that t he WANCY(HP) transcript is highly induced during anoxic exposure sugge sts that it may play an important role in the regulation of mitochondr ial activities to coordinate the physiological adaptation to anoxia.