H2Bub1

H2Bub1 refers to the protein histone H2B that has been modified by the addition of a single ubiquitin molecule. This specific type of post-translational modification, known as ubiquitination, plays a crucial role in regulating gene expression and other cellular processes. Ubiquitin is a small protein that can be covalently attached to other proteins, altering their function, stability, or localization.

The ubiquitination of histone H2B at specific lysine residues, particularly lysine 120 in humans (K120), is a well-studied event. This modification is primarily carried out by E3 ubiquitin ligases, such as RNF20/RNF40, and reversed by deubiquitinating enzymes (DUBs). The presence or absence of H2Bub1 is dynamic and tightly controlled, reflecting the cell's response to various stimuli and developmental cues.

H2Bub1 is closely associated with actively transcribed genes. It is thought to facilitate the elongation phase of transcription by influencing chromatin structure and promoting the recruitment of other factors involved in gene expression. Specifically, H2Bub1 is a prerequisite for subsequent histone modifications like H3K4 methylation and H3K79 methylation, which are hallmarks of active transcription. Loss of H2Bub1 generally leads to transcriptional repression and affects chromatin organization. Research into H2Bub1 continues to uncover its multifaceted roles in epigenetics, DNA repair, and cell cycle regulation.