PRDM9 activity depends on HELLS and promotes local 5-hydroxymethylcytosine enrichment

Area of Science:

• Genetics
• Epigenetics
• Molecular Biology

Background:

• Meiotic recombination initiates with DNA double-strand breaks (DSBs) at PRDM9-bound genomic locations.
• The molecular mechanisms linking PRDM9 binding to DSB formation remain largely unelucidated.
• Understanding these early steps is critical for comprehending genome stability and inheritance.

Purpose of the Study:

• To identify molecular partners of PRDM9 involved in initiating meiotic recombination.
• To investigate the role of identified partners in PRDM9 binding, DSB formation, and epigenetic modifications at recombination hotspots.
• To elucidate the sequence of events, including epigenetic changes and DSB activity, at PRDM9-specified sites.

Main Methods:

• Proteomic analysis to identify PRDM9-interacting proteins.
• Functional studies during mouse male meiosis.
• Analysis of DNA double-strand break (DSB) activity.
• Assessment of 5-hydroxymethylcytosine (5hmC) enrichment.
• Genetic analyses in mice deficient for SPO11 and PRDM9 methyltransferase.

Main Results:

• HELLS, a chromatin remodeler, was identified as a PRDM9 partner.
• HELLS is essential for PRDM9 binding and DSB formation specifically at PRDM9-dependent sites.
• HELLS is required for 5-hydroxymethylcytosine (5hmC) enrichment at PRDM9-bound regions.
• 5hmC enrichment occurs upon PRDM9 binding and histone modification, preceding DSB formation.

Conclusions:

• HELLS plays a critical role in establishing the chromatin and epigenetic landscape at PRDM9-specified meiotic recombination hotspots.
• The findings reveal a novel regulatory pathway involving HELLS in the initiation of meiotic recombination.
• Epigenetic modifications, including 5hmC, are established early and are independent of DSB activity at these sites.