histone H3 ubiquitin ligase activity

Definition

Target type: molecularfunction

Catalysis of the transfer of ubiquitin to a histone H3 substrate. [PMID:25303536]

Histone H3 ubiquitin ligase activity is a crucial regulatory mechanism in eukaryotes, playing a key role in chromatin remodeling and gene expression. This enzymatic activity involves the covalent attachment of ubiquitin, a small protein tag, to specific lysine residues within the N-terminal tail of histone H3. This modification, known as ubiquitination, alters the accessibility of DNA to transcription factors and other regulatory proteins, ultimately impacting gene expression.

Histone H3 ubiquitination can occur at multiple lysine residues, with different sites exhibiting distinct regulatory roles. For instance, ubiquitination at lysine 9 (H3K9) is typically associated with gene silencing, while ubiquitination at lysine 4 (H3K4) is generally linked to gene activation.

The process of histone H3 ubiquitination involves a multi-step cascade that requires a cascade of enzymes, including:

1. **Ubiquitin activating enzyme (E1):** This enzyme activates ubiquitin by attaching it to a high-energy cysteine residue.
2. **Ubiquitin conjugating enzyme (E2):** E2 receives ubiquitin from E1 and transfers it to a specific lysine residue on the target protein (in this case, histone H3)
3. **Ubiquitin ligase (E3):** This enzyme, also known as a ligase, recognizes and binds both the target protein (histone H3) and the ubiquitin-charged E2. It then facilitates the transfer of ubiquitin from E2 to the histone H3 substrate.

The specific E3 ligases responsible for histone H3 ubiquitination vary depending on the target lysine residue and the cellular context. Different E3 ligases can regulate the dynamics and spatial distribution of histone H3 ubiquitination, contributing to diverse cellular processes.

Histone H3 ubiquitination can be reversed by deubiquitinases, a class of enzymes that remove ubiquitin from proteins. This dynamic interplay between ubiquitination and deubiquitination ensures tight regulation of chromatin structure and gene expression.

In summary, histone H3 ubiquitin ligase activity is a critical regulatory mechanism that influences gene expression by controlling chromatin accessibility. The attachment of ubiquitin to histone H3 can alter chromatin compaction, recruit specific proteins, and fine-tune the transcription process. This enzymatic activity is tightly regulated and dynamically modulated by a complex interplay of E3 ligases and deubiquitinases, ensuring precise control over gene expression and cellular function.'
"

Proteins (1)

Compounds (2)