GENETIC AND MOLECULAR ANALYSIS OF A TRNA(LEU) MISSENSE SUPPRESSOR OF NUDC3, A MUTATION THAT BLOCKS NUCLEAR MIGRATION IN ASPERGILLUS-NIDULANS

NudC encodes a protein of unknown biochemical function that is require d for nuclear migration. In an attempt to define its function by ident ifying interacting proteins, a screen for extragenic suppressors of th e temperature-sensitive nudC3 mutation was undertaken that identified nine snc genes. Here we demonstrate that nudC3 has a missense mutation at amino acid 146 that causes leucine to be replaced by proline and t hat sncB69 encodes a mutant tRNA(Leu) that corrects the mutation. The sncB69 mutation deletes a single nucleotide in the anticodon of a tRNA (Leu) that changes its normal (5')CAG(3') leucine anticodon to the pro line anticodon (5')CGG(3'), which presumably allows incorporation of l eucine at the mutant nudC3 proline codon 146 and thereby causes suppre ssion of the nudC3 mutant phenotype.