title: Q/R RNA editing of the AMPA receptor subunit 2 (GRIA2) transcript evolves no later than the appearance of cartilaginous fishes.
abstract: The amino acid, either a glutamine (Q) or an arginine (R), at the Q/R site of the pore-lining segment (M2) of a vertebrate AMPA receptor subunit critically influences the properties of the receptor. The R codon of the mammalian AMPA receptor subunit 2 (GRIA2) transcript is not coded by the chromosomal sequence, but is created by posttranscriptional RNA editing activities. On the other hand, the R codons of some teleost GRIA2 homologs are coded by chromosomal sequences. To elucidate the evolution of the utilization of Q/R RNA editing in modifying vertebrate GRIA2 transcripts, the GRIA2 genes of five fish species and an amphibian were studied. The putative hagfish GRIA2 homolog (hfGRIA2) encodes an R codon, whereas shark and bullfrog GRIA2 genes specify a Q codon at the genomic Q/R site. All gnathostoma GRIA2 genes possess an intron splitting the coding regions of M2 and the third hydrophobic region (M3). The intronic components required for Q/R RNA editing are preserved in all the Q-coding vertebrate GRIA2 genes but are absent from the R-coding GRIA2 genes. Interestingly, the hfGRIA2 is intronless, suggesting that hfGRIA2 is unlikely evolved from a Q/R editing-competent gene. Results of this study suggest that modification of GRIA2 transcripts by Q/R editing is most likely acquired after the separation of the Agnatha and Gnathostome.
authors.affiliation: Department of Life Science, National Tsing-Hua University, 101, Sec 2, Kang Fu Road, 30043, Hsinchu, Taiwan, ROC.
authors.forename: S S
authors.initials: SS
authors.lastname: Kung
authors.forename: Y C
authors.initials: YC
authors.lastname: Chen
authors.forename: W H
authors.initials: WH
authors.lastname: Lin
authors.forename: C C
authors.initials: CC
authors.lastname: Chen
authors.forename: W Y
authors.initials: WY
authors.lastname: Chow
mesh_terms: D000818:Animals; D001120:Arginine / Q000235:genetics*; D004284:Dogfish / Q000235:genetics; D019143:Evolution, Molecular; D005973:Glutamine / Q000235:genetics*; D006196:Hagfishes / Q000235:genetics; D009690:Nucleic Acid Conformation; D021122:Protein Subunits; D017393:RNA Editing; D011892:Rana catesbeiana / Q000235:genetics; D018091:Receptors, AMPA / Q000235:genetics*; D023721:Tetraodontiformes / Q000235:genetics; D017210:Tilapia / Q000235:genetics; D015027:Zebrafish / Q000235:genetics
chemical_list: D021122:Protein Subunits; D018091:Receptors, AMPA; D005973:Glutamine; D001120:Arginine; C104722:glutamate receptor ionotropic, AMPA 2