Processivity and specificity of histone acetylation by the male-specific lethal complex

Area of Science:

• Epigenetics and Molecular Biology
• Chromatin Dynamics
• Gene Regulation

Background:

• Histone acetylation, particularly H4K16ac, is crucial for chromatin decondensation and transcriptional regulation.
• The MOF (KAT8) enzyme, a metazoan acetyltransferase, plays a key role in H4K16 acetylation.
• Previous antibody-based studies provided inconclusive data on MOF's substrate selectivity.

Purpose of the Study:

• To investigate the substrate selectivity of the MOF enzyme within the 4-MSL complex.
• To elucidate the mechanism of H4 N-terminus acetylation by MOF.
• To understand the role of RNA in modulating MOF activity and H4 acetylation patterns.

Main Methods:

• Utilized targeted mass spectrometry to analyze MOF activity on nucleosome array substrates.
• Employed mathematical modeling to interpret enzyme kinetics and acetylation patterns.
• Investigated the effect of RNA on MOF activity in vitro.

Main Results:

• MOF demonstrated high selectivity for H4K16 acetylation under short reaction times.
• Extended incubation led to processive acetylation of additional H4 lysines (H4K12, H4K8, H4K5).
• RNA addition suppressed non-specific H4 oligo-acetylation, promoting selective H4K16 acetylation.

Conclusions:

• MOF exhibits initial high selectivity for H4K16 but can exhibit processive acetylation of other lysines.
• RNA appears to enhance MOF's substrate turnover in vivo, limiting processivity and increasing H4K16 specificity.
• This finding provides insights into the regulation of gene expression through precise histone modification patterns.