Small-subunit processome, Utp13 (IPR013934)

Short name: SSU_processome_Utp13

Overlapping homologous superfamilies


Domain relationships



A large ribonuclear protein complex is required for the processing of the small-ribosomal-subunit rRNA - the small-subunit (SSU) processome [PMID: 12068309, PMID: 15590835]. This preribosomal complex contains the U3 snoRNA and at least 40 proteins, which have the following properties:

  • They are nucleolar.
  • They are able to coimmunoprecipitate with the U3 snoRNA and Mpp10 (a protein specific to the SSU processome).
  • They are required for 18S rRNA biogenesis.

There appears to be a linkage between polymerase I transcription and the formation of the SSU processome; as some, but not all, of the SSU processome components are required for pre-rRNA transcription initiation. These SSU processome components have been termed t-Utps. They form a pre-complex with pre-18S rRNA in the absence of snoRNA U3 and other SSU processome components. It has been proposed that the t-Utp complex proteins are both rDNA and rRNA binding proteins that are involved in the initiation of pre18S rRNA transcription. Initially binding to rDNA then associating with the 5' end of the nascent pre18S rRNA. The t-Utpcomplex forms the nucleus around which the rest of the SSU processome components, including snoRNA U3, assemble [PMID: 15489292]. From electron microscopy the SSU processome may correspond to the terminal knobs visualized at the 5' ends of nascent 18S rRNA.

Utp13 is a nucleolar protein and component of the small subunit (SSU) processome containing the U3 snoRNA that is involved in processing of pre-18S rRNA [PMID: 12068309].

Upt13 is also a component of the Pwp2 complex that forms part of a stable particle subunit independent of the U3 small nucleolar ribonucleoprotein that is essential for the initial assembly steps of the 90S pre-ribosome [PMID: 15231838]. Components of the Pwp2 complex are: Utp1 (Pwp2), Utp6, Utp12 (Dip2), Utp13, Utp18, and Utp21. The relationship between the Pwp2 complex and the t-Utps complex [PMID: 15489292] that also associates with the 5' end of nascent pre-18S rRNA is unclear.

GO terms

Biological Process

GO:0006364 rRNA processing

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0032040 small-subunit processome

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.