Nuclear pore proteins are involved in the biogenesis of functional tRNA.

Abstract

Los1p and Pus1p, which are involved in tRNA biogenesis, were found in a genetic screen for components interacting with the nuclear pore protein Nsp1p. LOS1, PUS1 and NSP1 interact functionally, since the combination of mutations in the three genes causes synthetic lethality. Pus1p is an intranuclear protein which exhibits a nucleotide‐specific and intron‐dependent tRNA pseudouridine synthase activity. Los1p was shown previously to be required for efficient pre‐tRNA splicing; we report here that Los1p localizes to the nuclear pores and is linked functionally to several components of the tRNA biogenesis machinery including Pus1p and Tfc4p. When the formation of functional tRNA was analyzed by an in vivo assay, the los1(‐) pus1(‐) double mutant, as well as several thermosensitive nucleoporin mutants including nsp1, nup116, nup133 and nup85, exhibited loss of suppressor tRNA activity even at permissive temperatures. These data suggest that nuclear pore proteins are required for the biogenesis of functional tRNA.

A stress response pathway from the endoplasmic reticulum to the nucleus requires a novel bifunctional protein kinase/endoribonuclease (Ire1p) in mammalian cells

“…The luciferase activity was determined from triplicate independent transfection experiments and was normalized to ␤-galactosidase activity to correct for transfection efficiency. also localized to the nucleoplasmic side of the nuclear pore (Simos et al 1996).…”

The Specificities of Four Yeast Dihydrouridine Synthases for Cytoplasmic tRNAs

“…In yeast, the only other known members of this class are Trm7p, which catalyzes 2Ј-O-methylation at positions 32 and 34 (29), and Pus3p, which forms ⌿ 38 and ⌿ 39 (30). Other modification enzymes act either at multiple sites, like Pus1p (6,31,32) and Trm4 (33), or, more commonly, at single sites. This region specificity argues either for conformational flexibility between the protein binding site and the active site or a flexible region of the tRNA substrate.…”

The essential Gcd10p–Gcd14p nuclear complex is required for 1-methyladenosine modification and maturation of initiator methionyl-tRNA

“…The fact that large fractions of Gcd10p and Gcd14p are found in the nucleus, where enzymes involved in modification (Rose et al 1995;Simos et al 1996) and processing (Clark and Abelson 1987) of tRNAs generally reside, suggests that they function directly in one or more aspects of tRNA i Met maturation. Gcd14p contains motifs (Kagan and Clarke 1994) common to S-adenosylmethionine-dependent methyltransferases (Cuesta et al in prep.…”