Human O-GlcNAcase catalytic-stalk dimer anchors flexible histone binding domains

Area of Science:

• Biochemistry
• Structural Biology
• Epigenetics

Background:

• O-linked N-acetylglucosamine (O-GlcNAc) modification is crucial for numerous cellular processes, yet the recognition mechanisms of its cycling enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), are not fully understood.
• Understanding OGA's substrate specificity is key to deciphering the biological roles of O-GlcNAcylation.

Purpose of the Study:

• To elucidate the molecular structure of the long isoform of human OGA (OGA-L) using cryo-electron microscopy (cryo-EM).
• To investigate the binding interactions of OGA-L with modified histone tails and nucleosomes.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to determine the high-resolution structure of OGA-L.
• Histone peptide arrays and recombinant mononucleosomes were used to assess OGA-L binding affinities.
• Chromatin immunoprecipitation (ChIP) experiments validated specific OGA-L-histone interactions in cells.

Main Results:

• The cryo-EM structure of OGA-L was solved, revealing its catalytic-stalk dimer and flexible pHAT domains.
• OGA-L demonstrated high-affinity binding to H3K36^Me3 and H4K^5,8,12,16Ac modified nucleosomes.
• Binding was specific to histone marks associated with open chromatin, not repressive marks.

Conclusions:

• OGA-L functions as a 'reader' of specific histone modifications, particularly those linked to active chromatin states.
• This interaction suggests a role for OGA-L in processes such as development, transcriptional activation, and DNA repair.