Lysine 2-hydroxyisobutyrylation is a widely distributed active histone mark

Area of Science:

• Epigenetics
• Molecular Biology
• Biochemistry

Background:

• Histone modifications regulate gene expression and chromatin structure.
• Lysine acetylation (Kac) and crotonylation (Kcr) are well-studied marks.
• The functional significance of other lysine modifications remains largely unexplored.

Purpose of the Study:

• To identify and characterize novel histone modifications.
• To investigate the role of new histone marks in male germ cell differentiation.
• To understand the relationship between different histone marks and gene transcription.

Main Methods:

• Mass spectrometry (MS) for initial identification of lysine 2-hydroxyisobutyrylation (Khib).
• Chemical and biochemical validation of the Khib mark.
• Chromatin immunoprecipitation sequencing (ChIP-seq) to determine genomic distribution.
• Gene expression analysis and immunodetection to assess functional roles.

Main Results:

• Identified Khib at 63 human and mouse histone sites, including 27 unique lysine sites.
• Khib exhibits distinct genomic distributions compared to Kac and Kcr during male germ cell differentiation.
• H4K8hib is associated with active gene transcription in meiotic and post-meiotic cells, encompassing H4K8ac-associated genes.
• The Khib mark is conserved, widely distributed, has high stoichiometry, and induces significant structural changes.

Conclusions:

• Lysine 2-hydroxyisobutyrylation (Khib) is a newly identified, conserved, and functionally significant histone modification.
• Khib plays a critical role in regulating chromatin functions, particularly in male germ cell development.
• This discovery expands our understanding of the epigenetic landscape and its role in cellular differentiation.