title: Evidence that the recently discovered theta 1-globin gene is functional in higher primates.
abstract: A new subfamily of the alpha-globin-like family has recently been identified in higher primates, rabbit, galago and possibly the horse. One member of this subfamily, theta 1, is downstream from the adult alpha 1-globin gene. In orang-utan, but not in rabbit or galago, the theta 1-gene appears to be structurally intact, suggesting that it may be functional in this species. The orang-utan theta 1-gene possesses initiation and termination codons, and the predicted polypeptide differs from the orang-utan alpha 1-globin by 55 amino acids. The upstream promoter boxes CCAAT and ATA are present, although approximately 150 base pairs (bp) farther upstream than in the alpha 1-gene. This structural difference in the promoter between the orang-utan theta 1- and alpha 1-genes has led Proudfoot to speculate that the theta 1-gene may be inactive. We have now cloned the theta 1- and alpha 1-globin genes from the olive baboon, and have compared their sequences with those of orang-utan. The unique promoter structure of the orang-utan theta 1-gene is highly conserved in baboon, although the orang-utan and baboon diverged nearly 30 million years ago. The coding sequences of the two theta 1-genes differ by only 6.3% with 22 out of 27 nucleotide substitutions being codon third position silent changes. These data support the view that the theta 1-gene has been functional in the baboon, orang-utan, and by implication, in man. We also estimate that the duplication event generating the theta 1- and alpha-globin-like subfamilies may have occurred as much as 260 million years ago.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D005701:Galago / Q000235:genetics; D005796:Genes; D005914:Globins / Q000235:genetics*; D006736:Horses / Q000235:genetics; D006801:Humans; D010215:Papio / Q000235:genetics; D010802:Phylogeny; D011148:Pongo pygmaeus / Q000235:genetics; D011323:Primates / Q000235:genetics*; D011817:Rabbits; D013045:Species Specificity
chemical_list: D005914:Globins