NAN1/YPL126W Summary Help

Standard Name NAN1 1
Systematic Name YPL126W
Alias UTP17 2
Feature Type ORF, Verified
Description U3 snoRNP protein; component of the small (ribosomal) subunit (SSU) processosome containing U3 snoRNA; required for the biogenesis of18S rRNA (1, 2 and see Summary Paragraph)
Name Description Net1 Associated Nuclear protein 1
Chromosomal Location
ChrXVI:310210 to 312900 | ORF Map | GBrowse
Gene Ontology Annotations All NAN1 GO evidence and references
  View Computational GO annotations for NAN1
Molecular Function
Manually curated
Biological Process
Manually curated
Cellular Component
Manually curated
Regulators 5 genes
Classical genetics
Large-scale survey
158 total interaction(s) for 72 unique genes/features.
Physical Interactions
  • Affinity Capture-MS: 141
  • Affinity Capture-RNA: 3
  • Affinity Capture-Western: 8
  • Co-fractionation: 1
  • Two-hybrid: 4

Genetic Interactions
  • Synthetic Lethality: 1

Expression Summary
Length (a.a.) 896
Molecular Weight (Da) 101,236
Isoelectric Point (pI) 6.32
Phosphorylation PhosphoGRID | PhosphoPep Database
sequence information
ChrXVI:310210 to 312900 | ORF Map | GBrowse
Last Update Coordinates: 2011-02-03 | Sequence: 1996-07-31
Subfeature details
Most Recent Updates
Coordinates Sequence
CDS 1..2691 310210..312900 2011-02-03 1996-07-31
Retrieve sequences
Analyze Sequence
S288C only
S288C vs. other species
S288C vs. other strains
External Links All Associated Seq | Entrez Gene | Entrez RefSeq Protein | MIPS | Search all NCBI (Entrez) | UniProtKB
Primary SGDIDS000006047

About the early stages of rRNA processing and 40S small ribosomal subunit assembly

The early stages of ribosome assembly occur in conjunction with processing of the 35S pre-ribosomal RNA transcript into the mature 18S, 5.8S, and 25S rRNA molecules. The first three cleavages at A0, A1, and A2 (see diagram) are essential for production of the 18S rRNA and the 40S small ribosomal subunit, but mutations which interfere with these cleavages have little effect on production of the 60S large ribosomal subunit (3). These three early cleavages occur in a series of large U3-associated ribonucleoprotein complexes (4, 5) and require base pairing of the U3 snoRNA with sequences in the 5'-ETS and the 18S rRNA (6, 7).

Click on the following figure for more details about the rDNA repeat and cleavage sites within the rRNA transcript:

figure 1

About the 90S preribosome and SSU processome complexes

A number of U3-containing early ribosome assembly and rRNA processing complexes have been identified that contain the 35S pre-rRNA transcript and have overlapping but not identical protein compositions (4, 5). Both the 90S preribosome and the small subunit (SSU) processome complexes contain ribosomal proteins, primarily of the small subunit, and non-ribosomal proteins presumably involved in rRNA processing and assembly of the small 40S ribsomal subunit. While many proteins are found in both complexes, some are found in only one or the other (see lists below). It may be that the 90S preribosome and SSU processome complexes are both intermediates in a series of complexes leading to the assembly of the small ribosomal subunit (4), or it may be that the SSU processome lies on an alternate assembly pathway (5).

The 90S preribosome complex is described as corresponding to the earliest detectable rRNA processing and ribosome assembly complex (8). The 90S is itself assembled from a number of stable subcomplexes including the t-UTP subcomplex (Utp5p, Utp4p, Nan1p, Utp8p, Utp9p, Utp10p, and Utp15p), the Pwp2p/UTP-B subcomplex (Utp6p, Pwp2p, Utp18p, Utp21p, Utp13p, and Dip2p) which interacts directly with the 5'-ETS of the 35S pre-rRNA (9), the UTP-C subcomplex (Rrp7p, Utp22p, Ckb1p, Cka1p, Ckb2p, and Cka2p), and the Mpp10 subcomplex (Mpp10p, Imp3p, and Imp4p) (10). The t-UTP subcomplex is also found as part of the SSU processome complex, which is slightly smaller at 80S (2, 11). Depletion of any of the members of the t-UTP subcomplex results in decreased transcription of rDNA leading to decreased levels of the primary 35S rRNA transcript (12). In contrast, mutation or depletion of most other members of either the 90S preribosome or SSU processome complexes causes decreased 18S rRNA levels without affecting the levels of the 25S or 5.8S rRNAs.

Non-ribosomal protein components of the 90S preribosome and SSU processome

Subunits of both the 90S preribosome (8) and SSU processome (2, 11) include: Bud21p, Dip2p, Ecm16p, Emg1p, Imp3p, Imp4p, Krr1p, Mpp10p, Nan1p, Noc4p, Nop1p, Nop14p, Nop58p, Pwp2p, Rrp5p, Rrp9p, Nop56p, Sof1p, Utp4p, Utp6p, Utp7p, Utp8p, Utp9p, Utp10p, Utp13p, Utp15p, Utp18p, Utp20p, Utp21p, and Utp22p

Additional subunits of the 90S preribosome (8) include: Bfr2p, Bms1p, Cbf5p, Cms1p, Dbp8p, Dim1p, Enp1p, Enp2p, Has1p, Kre33p, Mrd1p, Nop9p (13), Pno1p, Prp43p, Rcl1p, Rok1p, Rrp12p, Scl1p, Slx9p (14), Tsr1p, and Utp30p

Additional subunits of the SSU processome (2, 11) include: Fcf1p, Utp23p, Sas10p, Snu13p, Utp5p, Utp11p, and Utp14p

Last updated: 2008-07-17 Contact SGD

References cited on this page View Complete Literature Guide for NAN1
1) Shou W, et al.  (1999) Exit from mitosis is triggered by Tem1-dependent release of the protein phosphatase Cdc14 from nucleolar RENT complex. Cell 97(2):233-44
2) Dragon F, et al.  (2002) A large nucleolar U3 ribonucleoprotein required for 18S ribosomal RNA biogenesis. Nature 417(6892):967-70
3) Venema J and Tollervey D  (1999) Ribosome synthesis in Saccharomyces cerevisiae. Annu Rev Genet 33:261-311
4) Fromont-Racine M, et al.  (2003) Ribosome assembly in eukaryotes. Gene 313:17-42
5) Granneman S and Baserga SJ  (2004) Ribosome biogenesis: of knobs and RNA processing. Exp Cell Res 296(1):43-50
6) Beltrame M and Tollervey D  (1995) Base pairing between U3 and the pre-ribosomal RNA is required for 18S rRNA synthesis. EMBO J 14(17):4350-6
7) Hughes JM  (1996) Functional base-pairing interaction between highly conserved elements of U3 small nucleolar RNA and the small ribosomal subunit RNA. J Mol Biol 259(4):645-54
8) Grandi P, et al.  (2002) 90S pre-ribosomes include the 35S pre-rRNA, the U3 snoRNP, and 40S subunit processing factors but predominantly lack 60S synthesis factors. Mol Cell 10(1):105-15
9) Dosil M and Bustelo XR  (2004) Functional characterization of Pwp2, a WD family protein essential for the assembly of the 90 S pre-ribosomal particle. J Biol Chem 279(36):37385-97
10) Perez-Fernandez J, et al.  (2007) The 90S preribosome is a multimodular structure that is assembled through a hierarchical mechanism. Mol Cell Biol 27(15):5414-29
11) Bernstein KA, et al.  (2004) The small-subunit processome is a ribosome assembly intermediate. Eukaryot Cell 3(6):1619-26
12) Gallagher JE, et al.  (2004) RNA polymerase I transcription and pre-rRNA processing are linked by specific SSU processome components. Genes Dev 18(20):2506-17
13) Thomson E, et al.  (2007) Nop9 is an RNA binding protein present in pre-40S ribosomes and required for 18S rRNA synthesis in yeast. RNA 13(12):2165-2174
14) Bax R, et al.  (2006) Slx9p facilitates efficient ITS1 processing of pre-rRNA in Saccharomyces cerevisiae. RNA 12(11):2005-13