H2B ubiquitylation: the end is in sight.

Area of Science:

• Molecular Biology
• Epigenetics
• Yeast Genetics

Background:

• Histone H2A was the first eukaryotic protein identified as ubiquitylated in 1975.
• Ubiquitylated histones (H1, H2A, H2B, H3, H2A.Z) are found across eukaryotes.
• Research on histone ubiquitylation has recently surged due to new genetic systems and discoveries.

Purpose of the Study:

• To review recent findings on the regulation and cellular roles of histone H2B ubiquitylation in yeast.
• To highlight the significance of H2B ubiquitylation in trans-histone methylation and gene expression.

Main Methods:

• Utilized the budding yeast *Saccharomyces cerevisiae* as a model organism due to its tractable genetics.
• Focused on monoubiquitylation, a form of ubiquitin conjugation not typically associated with protein degradation.
• Reviewed recent discoveries linking H2B ubiquitylation to histone H3 methylation.

Main Results:

• Histone H2B ubiquitylation was identified in *S. cerevisiae* in 2000, providing a robust genetic system for study.
• Monoubiquitylation of histones, unlike polyubiquitylation, does not primarily target proteins for degradation.
• Ubiquitylated H2B plays a critical role in the trans-histone methylation of histone H3.

Conclusions:

• Histone H2B ubiquitylation is a key epigenetic mark involved in regulating gene expression.
• The study of H2B ubiquitylation in yeast has provided significant insights into its cellular functions.
• This modification is integral to the interplay between different histone modifications, such as methylation.