Hypoxia-inducible factor-1 alpha in Antarctic notothenioids contains a polyglutamine and glutamic acid insert that varies in length with phylogeny

摘要

The long evolution of the Antarctic perciform suborder of Notothenioidei in the icy, oxygen-rich waters of the Southern Ocean may have reduced selective pressure to maintain a hypoxic response. To test this hypothesis, cDNA of the key transcriptional regulator of hypoxic genes, hypoxia-inducible factor-1 alpha (HIF-1 alpha), was sequenced in heart ventricles of the red-blooded notothenioid, Notothenia coriiceps, and the hemoglobinless icefish, Chaenocephalus aceratus. HIF-1 alpha cDNA is 4500 base pairs (bp) long and encodes 755 amino acids in N. coriiceps, and in C. aceratus, HIF-1 alpha is 3576 bp long and encodes 779 amino acids. All functional domains of HIF-1 alpha are highly conserved compared to other teleosts, but HIF-1 alpha contains a polyglutamine/glutamic acid (polyQ/E) insert nine amino acids long in N. coriiceps and 34 amino acids long in C. aceratus. Sequencing of this region in four additional species, representing three families of notothenioids, revealed that the length of the polyQ/E insert varies with phylogeny. Icefishes, the crown family of notothenioids, contain the longest polyQ/E inserts, ranging between 16 and 34 amino acids long, whereas the basal, cold-temperate notothenioid, Eleginops maclovinus, contains a polyQ/E insert only 4 amino acids long. PolyQ/E inserts may affect dimerization of HIF-1 alpha and HIF-1 beta, HIF-1 translocation into the nucleus and/or DNA binding.