Structural insights into a novel histone demethylase PHF8

Area of Science:

• Biochemistry
• Structural Biology
• Developmental Biology

Background:

• Dynamic regulation of histone methylation/demethylation is crucial for development.
• Mutations in human plant homeodomain (PHD) finger protein 8 (PHF8) are linked to X-linked mental retardation and distinct facial anomalies.
• The precise molecular function and structural basis of PHF8's role in these conditions remain largely unknown.

Purpose of the Study:

• To elucidate the molecular function and structural basis of human PHF8.
• To investigate PHF8's substrate specificity and mechanism of action.
• To understand the link between PHF8 mutations and associated pathologies.

Main Methods:

• High-resolution crystal structure determination of the PHF8 catalytic core.
• Biochemical assays to assess histone demethylase activity.
• In vitro demethylation assays using wild-type and mutant PHF8.

Main Results:

• The crystal structures of the PHF8 catalytic core were determined with and without alpha-ketoglutarate.
• PHF8 was identified as a novel histone demethylase specific for H3K9me2/1, but not H3K9me3.
• A patient-observed F279S mutant showed complete loss of demethylation activity, implicating enzymatic dysfunction in disease pathogenesis.

Conclusions:

• PHF8 functions as a specific H3K9me2/1 demethylase, with its structure providing insights into methylation state discrimination.
• Loss of PHF8 demethylase activity is a key factor in the pathogenesis of PHF8-associated developmental and neurological disorders.
• These findings offer a molecular basis for understanding PHF8-related diseases.