NoRC complex

Definition

Target type: cellularcomponent

An ISWI complex that contains an ATPase subunit of the ISWI family (specifically SNF2H in mammals, which contain two ISWI homologs) and a Tip5 homolog. In mammals, NoRC is involved in regulation of transcription from RNAP I and RNA polymerase III promoters. [GOC:krc]

The NoRC complex (nucleolar remodeling complex) is a multi-protein complex that plays a crucial role in ribosomal DNA (rDNA) transcription, nucleolar structure, and the maintenance of genomic stability. It is found primarily in the nucleolus, a specialized structure within the nucleus responsible for ribosome biogenesis. The core components of the NoRC complex include:

- **TCOF1 (Treacle):** This protein acts as a scaffolding component and directly interacts with rDNA. It also recruits other NoRC components, including Nopp140.
- **Nopp140:** This nucleolar phosphoprotein interacts with TCOF1 and contributes to rDNA transcription regulation. It is involved in the assembly of the pre-ribosomal RNA (pre-rRNA) processing machinery and the formation of nucleolar structures.
- **Nol11:** This protein interacts with Nopp140 and TCOF1, and it plays a role in regulating rDNA transcription by promoting the recruitment of RNA polymerase I.
- **Rrn3:** This protein acts as a nucleolar chaperone that facilitates the folding and assembly of pre-rRNA molecules.
- **Utp14C:** This protein is a component of the UTP complex, which is involved in the synthesis and processing of pre-rRNA.

In addition to these core components, the NoRC complex can also associate with other proteins, such as:

- **Histone H4:** This protein is involved in chromatin structure and regulation of rDNA transcription.
- **CAF-1 (chromatin assembly factor 1):** This complex is responsible for assembling nucleosomes, the basic building blocks of chromatin.
- **HDAC1 (histone deacetylase 1):** This enzyme removes acetyl groups from histones, leading to changes in chromatin structure and gene expression.

The NoRC complex is highly dynamic and its composition can vary depending on the cellular context. The precise function of each component within the complex is still under investigation, but it is clear that the NoRC complex is essential for maintaining the integrity and function of the nucleolus and the ribosome biogenesis pathway.'
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Proteins (1)

Compounds (1)