chromatin lock complex

Definition

Target type: cellularcomponent

A chromatin silencing complex that binds and bridges separate nucleosomal histones resulting in heterochromatin assembly and chromatin looping. [GOC:bhm, GOC:dph, PMID:17540172]

The chromatin lock complex is a multi-protein complex that plays a crucial role in regulating gene expression by preventing the accessibility of DNA to transcription factors. It acts as a barrier to the progression of RNA polymerase II (RNAPII) along the DNA template, effectively halting transcription. This complex is primarily localized within the nucleus, specifically associated with the chromatin, the complex of DNA and proteins that comprises chromosomes. The core components of the chromatin lock complex include:

1. **SETD2:** A histone methyltransferase responsible for trimethylating histone H3 at lysine 36 (H3K36me3), a modification that serves as a recognition site for the complex.
2. **MLL3/MLL4:** Trithorax group proteins that catalyze the methylation of histone H3 at lysine 4 (H3K4me3), another modification crucial for gene activation.
3. **SPT6:** A histone chaperone protein that aids in the deposition of histones onto DNA, playing a role in the structural integrity of chromatin.
4. **FACT:** A complex consisting of the proteins SSRP1 and Pob1, which facilitates the passage of RNAPII through nucleosomes, a basic unit of chromatin.
5. **Mediator complex:** A large multi-protein complex that functions as a bridge between transcription factors and RNAPII, enabling the initiation of transcription.

The complex assembles at specific genomic regions, usually near gene promoters, where it forms a physical barrier that restricts the access of RNAPII to the DNA template. This blockage of RNAPII movement can prevent transcriptional elongation and thereby regulate gene expression. The chromatin lock complex is believed to play a critical role in maintaining genomic stability and controlling the proper expression of genes.'
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Proteins (2)

Compounds (8)