BMI1s interact with condensin complexes to regulate chromatin 3D structure and gene expression in Arabidopsis

Area of Science:

• Epigenetics and Molecular Biology
• Plant Genomics and Chromosome Biology

Background:

• Accurate chromatin states are vital for genome integrity and gene transcription.
• Polycomb group (PcG) proteins, including PRC1 components like BMI1s, influence chromatin structure and modifications.
• The precise mechanism by which BMI1s maintain chromatin compartment domains (CDs) was previously unclear.

Purpose of the Study:

• To elucidate the mechanism by which BMI1s maintain chromatin compartment domains.
• To investigate the interaction between BMI1s and condensin complexes in regulating chromatin structure.
• To understand the combined role of BMI1s and condensin in gene expression and genome integrity.

Main Methods:

• Investigated interactions between BMI1s and condensin complexes.
• Utilized genetic mutants of BMI1s and condensin complexes (I and II) in Arabidopsis.
• Assessed chromatin compartment domain integrity using mutant lines.
• Analyzed gene expression and histone modification levels (H3K27me3, H2AK121ub).

Main Results:

• Condensin complexes interact with BMI1s.
• Loss of either BMI1s or condensin complexes leads to global impairment of chromatin compartment domains.
• The effects of BMI1 and condensin loss on CDs are similar, indicating cooperation.
• BMI1s and condensin complexes jointly regulate gene expression and may maintain genome integrity under stress.

Conclusions:

• BMI1s and condensin complexes cooperate to maintain chromatin compartment domains in Arabidopsis.
• This cooperation is parallel to histone modification pathways in maintaining CDs.
• The findings provide new insights into the epigenetic regulatory mechanisms of PRC1 beyond histone modifications.