A Tail-Based Mechanism Drives Nucleosome Demethylation by the LSD2/NPAC Multimeric Complex

Area of Science:

• Biochemistry
• Molecular Biology
• Epigenetics

Background:

• Lysine-specific demethylase 1 (LSD1) and LSD2 are homologous histone demethylases with opposing roles in gene regulation.
• LSD1 is associated with chromatin silencing, while LSD2 promotes transcription elongation.
• LSD2's nucleosome-demethylase activity is dependent on a linker peptide from the multidomain protein NPAC.

Purpose of the Study:

• To elucidate the mechanism of the human LSD2/NPAC-linker/nucleosome complex.
• To understand how LSD2 facilitates histone demethylation and transcription elongation.

Main Methods:

• Single-particle cryoelectron microscopy (cryo-EM).
• Kinetic analysis.
• Mutational analysis.

Main Results:

• LSD2 exhibits weak interactions with DNA, allowing multiple binding modes to the nucleosome.
• The complex efficiently demethylates mono- and dimethylated Lysine 4 on the H3 tail.
• The NPAC dehydrogenase domain acts as a catalytically inert oligomerization module.
• LSD2/NPAC, with its flexible linkers, is adapted for rapid chromatin modification during transcription elongation.

Conclusions:

• The LSD2/NPAC complex is structurally distinct from LSD1/CoREST, enabling dynamic interactions with actively transcribing genes.
• The flexible nature of LSD2/NPAC facilitates rapid chromatin modification, supporting RNA polymerase progression.
• This contrasts with the static LSD1/CoREST complex, which docks at silenced gene promoters.