RNA-binding protein NOB1 has a nuclear location []and contains a PIN domain and binds a single zinc ion. Budding yeast Nob1 is involved in proteasomal and 40S ribosomal subunit biogenesis []. It is also required for maturation of the small subunit ribosomal RNA by catalyzing cleavage at site D after export of the preribosomal subunit into the cytoplasm. Nob1 is also found in archaea, where it is manganese-dependent and also processes RNA-substrates []. This entry also includes VapC1 and VapC3. VapC1 is a toxic component and a ribonuclease of a toxin-antitoxin (TA) module [].
Pre-rRNA-processing protein PNO1 is also known as Partner of NOB1 and ribosomal RNA-processing protein 20. NOB1 is a nuclear protein that forms a complex with the 19S regulatory particle of the 26S proteasome and PNO1, acting as a chaperone to join the 20S proteasome with the 19S regulatory particle. The NOB1 complex is then degraded by the mature 26S proteasome []. PNO1 is also a component of the pre-ribosomal particle, and strains lacking PNO1 are defective in ribosomal RNA processing []. PNO1 remains a component of the SSU RRP complex, in which pre-40S subunits are left associated with a limited set of proteins []. PNO1 contains a K Homology domain.
Budding yeast Nob1 is involved in proteasomal and 40S ribosomal subunit biogenesis. It is required for cleavage of the 20S pre-rRNA to generate the mature 18S rRNA [, , ].
This is a PIN domain found in eukaryotic ribonuclease Nob1 and archaeal ribonuclease VapC1 []. RNA-binding protein NOB1 has a nuclear location []and contains a PIN domain and binds a single zinc ion. Budding yeast Nob1 is involved in proteasomal and 40S ribosomal subunit biogenesis []. It is also required for maturation of the small subunit ribosomal RNA by catalyzing cleavage at site D after export of the preribosomal subunit into the cytoplasm. Nob1 is also found in archaea, where it is manganese-dependent and also processes RNA-substrates []. This domain can also be found in VapC1, which is a toxic component and a ribonuclease of a toxin-antitoxin (TA) module [].PIN domains are small protein domains identified by the presence of three strictly conserved acidic residues. Apart from these three residues, there is poor sequence conservation []. PIN domains are found in eukaryotes, eubacteria and archaea. In eukaryotes they are ribonucleases involved in nonsense mediated mRNA decay []and in processing of 18S ribosomal RNA []. In prokaryotes, they are the toxic components of toxin-antitoxin (TA) systems, their toxicity arising by virtue of their ribonuclease activity. The PIN domain TA systems are now called VapBC TAs(virulence associated proteins), where VapB is the inhibitor and VapC, the PIN-domain ribonuclease toxin [].
This entry represents the first K homology domain (KH1) in the KRR1 and Dim2 (Pno1) proteins.Krr1 and Dim2 are structurally related ribosomal assembly factors, present on the 90S pre-ribosome []. They both belong to the family of RNA binding domains that contain K homology (KH) domains. Dim2 and Krr1 each contain two sequential KH domains (KH1 and KH2), but the N and C-terminal extensions differ between the two proteins []. The two KH domains are evident in the structure of KKr1 from Saccharomyces Cerevisiae [].The KH1 domains in Krr1 and Dim2 lack the typical GXXG RNA binding motif and are involved, instead, in protein-protein interactions. The KH1 domain in Krr1 interacts with the nucleolar assembly factor Kri1 and the KH1 domain of Dim2 interacts with the endonuclease Nob1 [].
