title: Expanded HOXA13 polyalanine tracts in a monotreme.
abstract: The N-terminal region of human HOXA13 has seven discrete polyalanine tracts. Our previous analysis of these tracts in multiple major vertebrate clades suggested that three are mammal-specific. We now report the N-terminal HOXA13 repetitive tract structures in the monotreme Tachyglossus aculeatus (echidna). Contrary to our expectations, echidna HOXA13 possesses a unique set of polyalanine tracts and an unprecedented polyglycine tract. The data support the conclusion that the emergence of expanded polyalanine tracts in proteins occurred very early in the stem lineage that gave rise to mammals, between 162 and 315 Ma.
authors.affiliation: Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109-5618, USA.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Lehoczky
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Innis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D018398:Homeodomain Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D010802:Phylogeny; D020449:Repetitive Sequences, Amino Acid; D012098:Reproduction / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D004442:Tachyglossidae / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D010455:Peptides; C099959:homeobox protein HOXA13; C019529:polyalanine