title: Allele-specific suppressors of lin-1(R175Opal) identify functions of MOC-3 and DPH-3 in tRNA modification complexes in Caenorhabditis elegans.
abstract: The elongator (ELP) complex consisting of Elp1-6p has been indicated to play roles in multiple cellular processes. In yeast, the ELP complex has been shown to genetically interact with Uba4p/Urm1p and Kti11-13p for a function in tRNA modification. Through a Caenorhabditis elegans genetic suppressor screen and positional cloning, we discovered that loss-of-function mutations of moc-3 and dph-3, orthologs of the yeast UBA4 and KTI11, respectively, effectively suppress the Multivulva (Muv) phenotype of the lin-1(e1275, R175Opal) mutation. These mutations do not suppress the Muv phenotype caused by other lin-1 alleles or by gain-of-function alleles of ras or raf that act upstream of lin-1. The suppression can also be reverted by RNA interference of lin-1. Furthermore, we showed that dph-3(lf) also suppressed the defect of lin-1(e1275) in promoting the expression of a downstream target (egl-17). These results indicate that suppression by the moc-3 and dph-3 mutations is due to the elevated activity of lin-1(e1275) itself rather than the altered activity of a factor downstream of lin-1. We further showed that loss-of-function mutations of urm-1 and elpc-1-4, the worm counterparts of URM1 and ELP complex components in yeast, also suppressed lin-1(e1275). We also confirmed that moc-3(lf) and dph-3(lf) have defects in tRNA modifications as do the mutants of their yeast orthologs. These results, together with the observation of a likely readthrough product from a lin-1(e1275)::gfp fusion transgene indicate that the aberrant tRNA modification led to failed recognition of a premature stop codon in lin-1(e1275). Our genetic data suggest that the functional interaction of moc-3/urm-1 and dph-3 with the ELP complex is an evolutionarily conserved mechanism involved in tRNA functions that are important for accurate translation.
authors.affiliation: Howard Hughes Medical Institute and Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA.
authors.forename: Sunhong
authors.initials: S
authors.lastname: Kim
authors.forename: Wade
authors.initials: W
authors.lastname: Johnson
authors.forename: Changchun
authors.initials: C
authors.lastname: Chen
authors.forename: Aileen K
authors.initials: AK
authors.lastname: Sewell
authors.forename: Anders S
authors.initials: AS
authors.lastname: Byström
authors.forename: Min
authors.initials: M
authors.lastname: Han
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D015153:Blotting, Western; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007814:Larva / Q000235:genetics / Q000254:growth & development; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D034622:RNA Interference; D012343:RNA, Transfer / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; C097533:Lin-1 protein, C elegans; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D012343:RNA, Transfer