title: Cross-species and cross-compartmental aminoacylation of isoaccepting tRNAs by a class II tRNA synthetase.
abstract: It was previously shown that ALA1, the only alanyl-tRNA synthetase gene in Saccharomyces cerevisiae, codes for two functionally exclusive protein isoforms through alternative initiation at two consecutive ACG codons and an in-frame downstream AUG. We reported here the cloning and characterization of a homologous gene from Candida albicans. Functional assays show that this gene can substitute for both the cytoplasmic and mitochondrial functions of ALA1 in S. cerevisiae and codes for two distinct protein isoforms through alternative initiation from two in-frame AUG triplets 8-codons apart. Unexpectedly, although the short form acts exclusively in cytoplasm, the longer form provides function in both compartments. Similar observations are made in fractionation assays. Thus, the alanyl-tRNA synthetase gene of C. albicans has evolved an unusual pattern of translation initiation and protein partitioning and codes for protein isoforms that can aminoacylate isoaccepting tRNAs from a different species and from across cellular compartments.
authors.affiliation: Department of Life Science, National Central University, Jung-li, Taiwan 32001.
authors.forename: Hsiao-Yun
authors.initials: HY
authors.lastname: Huang
authors.forename: Yu
authors.initials: Y
authors.lastname: Kuei
authors.forename: Hen-Yi
authors.initials: HY
authors.lastname: Chao
authors.forename: Shun-Jia
authors.initials: SJ
authors.lastname: Chen
authors.forename: Lu-Shu
authors.initials: LS
authors.lastname: Yeh
authors.forename: Chien-Chia
authors.initials: CC
authors.lastname: Wang
mesh_terms: D000412:Alanine-tRNA Ligase / Q000737:chemistry*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002176:Candida albicans / Q000201:enzymology*; D003062:Codon; D018387:Codon, Initiator; D015966:Gene Expression Regulation, Fungal; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D020033:Protein Isoforms; D012343:RNA, Transfer / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D017386:Sequence Homology, Amino Acid
chemical_list: D003062:Codon; D018387:Codon, Initiator; D020033:Protein Isoforms; D012343:RNA, Transfer; D000412:Alanine-tRNA Ligase