PRC1 complex

Definition

Target type: cellularcomponent

A multiprotein complex that mediates monoubiquitination of lysine residues of histone H2A (lysine-118 in Drosophila or lysine-119 in mammals). The complex is required for stable long-term maintenance of transcriptionally repressed states and is involved in chromatin remodeling. [GOC:bf, PMID:10412979]

The Polycomb Repressive Complex 1 (PRC1) is a multi-protein complex that plays a crucial role in gene silencing and the maintenance of cellular identity. It is composed of several core subunits, including:

* **Chromobox (CBX) proteins:** These proteins bind to histone H3 trimethylated at lysine 27 (H3K27me3), a repressive histone modification. CBX proteins act as the “reader” module of PRC1, recognizing the H3K27me3 mark and targeting PRC1 to specific genomic regions. Examples include CBX2, CBX4, CBX6, CBX7, and CBX8.

* **RING1A/RING1B proteins:** These proteins are responsible for the enzymatic activity of PRC1, catalyzing the monoubiquitylation of histone H2A at lysine 119 (H2AK119ub1). This modification further silences gene expression by contributing to chromatin compaction and preventing access of transcriptional machinery to DNA.

* **Polycomb group (PCG) proteins:** These proteins, including PCGF2, PCGF3, PCGF4, and PCGF6, are involved in the assembly and stability of PRC1 complexes. They can bind to various other proteins, contributing to the diverse functions and compositions of different PRC1 subcomplexes.

* **Additional proteins:** Other proteins, such as SCMH1, RYBP, and PHC1, can associate with PRC1 and modulate its activity.

**Subcomplexes:**

The PRC1 complex can form various subcomplexes with distinct compositions and functions. Some common subcomplexes include:

* **Canonical PRC1:** Consists of CBX proteins, RING1A/B, PCGF proteins, and SCMH1.
* **Non-canonical PRC1:** Lacks CBX proteins but may include other proteins, such as RYBP and PHC1.

**Function:**

The PRC1 complex plays a vital role in:

* **Gene silencing:** It acts as a repressor of gene expression by catalyzing histone modifications and contributing to chromatin compaction.
* **Cellular development:** PRC1 is involved in the regulation of cell fate decisions and the maintenance of cellular identity.
* **Cellular proliferation and differentiation:** PRC1 plays a role in the control of cell cycle progression and the differentiation of various cell types.

**Disease relevance:**

Dysregulation of PRC1 function is associated with several diseases, including:

* **Cancer:** Deregulation of PRC1 can lead to uncontrolled cell proliferation and tumor formation.
* **Developmental disorders:** Mutations in PRC1 components can result in developmental defects and syndromes.

**Overall, the PRC1 complex is a dynamic and versatile protein complex that plays a critical role in regulating gene expression and cellular processes.**'"

Proteins (1)

Compounds (2)