This entry includes NOPCHAP1 from animals and New4 from fission yeast.NOPCHAP1 is a client-loading PAQosome/R2TP complex cofactor that selects NOP58 to promote box C/D small nucleolar ribonucleoprotein (snoRNP) assembly []. The function of New4 is not clear.
This entry includes a group of pre-RNA processing ribonucleoproteins (RNPs), including Nop56/Nop58 from animals and their homologue, Nop5, from archaea. Proteins in this family contains the Nop domain, which is a RNP binding module, exhibiting RNA and protein binding surfaces. It is oval-shaped and exclusively α-helical [, ]. Nop56 and Nop58 are components of box C/D small nucleolar ribonucleoprotein (snoRNP) particles [, ].
SPB1 is an adoMet-dependent rRNA methyltransferase required for proper assembly of pre-ribosomal particles during the biogenesis of the 60S ribosomal subunit []. In Saccharomyces cerevisiae, it specifically methylates the guanosine in position 2922 of the 25S rRNA at the stage of 27S pre-rRNA maturation []. It interacts with the snoRNA-associated proteins Nop1 and Nop58 []. FTSJ3, SPB1 homologue in humans, is associated with NIP7 (involved in the biogenesis of 40S subunit) and functions in pre-rRNA processing [].
This N-terminal domain is found in Nucleolar protein 58/56 from fungi and animals and the homologues form plants. These are RNA-binding proteins of the NOP5 family []. Nop56 and Nop58 are components of box C/D small nucleolar ribonucleoprotein (snoRNP) particles [, ]. This domain interacts with Nop1 and forms the box B/C side, in the case of Nop56, or box C'/D side in the case of Nop58, of U3 snoRNP [].
This uncharacterised domain is found in the central region of fungal SPB1 and mammalian homologue FTSJ3.SPB1 is an adoMet-dependent rRNA methyltransferase required for proper assembly of pre-ribosomal particles during the biogenesis of the 60S ribosomal subunit []. In Saccharomyces cerevisiae, it specifically methylates the guanosine in position 2922 of the 25S rRNA at the stage of 27S pre-rRNA maturation []. It interacts with the snoRNA-associated proteins Nop1 and Nop58 []. FTSJ3, SPB1 homologue in humans, is associated with NIP7 (involved in the biogenesis of 40S subunit) and functions in pre-rRNA processing [].
This domain is found at the C terminus SPB1-like proteins. This domain interacts with the meandering tail of Erb1 and its removal is required to form the pre-mature inter-subunit surface of the Arx1/Nog2 particle [, ].SPB1 is an adoMet-dependent rRNA methyltransferase required for proper assembly of pre-ribosomal particles during the biogenesis of the 60S ribosomal subunit []. In Saccharomyces cerevisiae, it specifically methylates the guanosine in position 2922 of the 25S rRNA at thestage of 27S pre-rRNA maturation []. It interacts with the snoRNA-associated proteins Nop1 and Nop58 []. FTSJ3, SPB1 homologue in humans, is associated with NIP7 (involved in the biogenesis of 40S subunit) and functions in pre-rRNA processing [].
SENP5 peptidase (sentrin-specific peptidase 5, MEROPS identifier C48.008) is a deSUMOylating peptidase localized predominantly to the nucleolus. SENP5 releases the tag proteins SUMO-2 and -3 from conjugates, preferentially acting as an isopeptidase rather than an endopeptidase []. Simultaneous depletion of SENP3 and SENP5 results in enhanced SUMOylation of proteins such as RPL37A and GNL2, which are involved in the processing of pre-rRNA [], PELP1 and LAS1L, which are involved in the release of mature ribosomal particles [], and Nop58, which is a component of small nucleolar ribonucleoprotein (snoRNP) and SUMOlyation is required for binding of Nop58 to snoRNA to maintain nucleolar retention []. SENP5 depletion also affects mitotic progression, and cells arrest at the G2/M transition []. SENP5 is also involved in mitochondrial fusion and fission, because SUMOylated dynamin-1-like protein (Drp1), which is a mitochondrial fission factor, is a target for SENP5 []. DeSUMOylation of Drp1 is a contributory factor to cardiomyopathy []. During the G2/M transition stage of mitosis, SENP5 transiently locates to the mitochondrion []. SENP5 is also required for neutrophil differentiation, and the SNP5 gene is repressed in clinical acute myeloid leukemia [].
