Nin One Binding Protein (NOB1)

Nob1 is involved in pre-rRNA processing. In a late cytoplasmic processing step, Nob1 cleaves a 20S rRNA intermediate at cleavage site D to produce the mature 18S rRNA. The deduced 412-amino acid human protein shares significant homology with yeast Nob1 and its eukaryotic orthologs, including a highly conserved PIN domain, which is predicted to be involved in RNA degradation, and complete conservation of 4 cysteines in the metal-binding zinc ribbon domain. Immunofluorescence microscopy of yeast detected Nob1 in both the nucleus and cytoplasm. Nob1 associated with pre-40S ribosomal particles. Conditional Nob1 knockout in yeast led to accumulation of the 20S rRNA intermediate and a block in processing of the 20S pre-rRNA to the mature 18S rRNA.