InterPro domain: IPR039844

Nucleolar pre-ribosomal-associated protein 1 (Npa1) is required for ribosome biogenesis and operates in the same functional environment as Rsa3p and Dbp6p during early maturation of 60S ribosomal subunits [ 1 ]. The protein partners of Npa1p include eight putative helicases as well as the novel Npa2p factor. Npa1p can also associate with a subset of H/ACA and C/D small nucleolar RNPs (snoRNPs) involved in the chemical modification of residues in the vicinity of the peptidyl transferase centre [ 2 ]. The protein has also been referred to as Urb1.

1. Npa1p is an essential trans-acting factor required for an early step in the assembly of 60S ribosomal subunits in Saccharomyces cerevisiae. RNA 10, 1073-83
2. Npa1p, a component of very early pre-60S ribosomal particles, associates with a subset of small nucleolar RNPs required for peptidyl transferase center modification. Mol. Cell. Biol. 24, 6324-37