RNAPII and DNA supercoiling regulate cohesin engagement in neurons

Area of Science:

• Molecular Biology
• Genetics
• Neuroscience

Background:

• Chromatin looping mediated by CTCF and cohesin is vital for chromosome organization and gene transcription.
• The specific roles of CTCF, cohesin, and transcription in neurons remain unclear.

Purpose of the Study:

• To investigate the relationship between CTCF, cohesin, and transcriptionally engaged RNA polymerase II (RNAPII) in mouse cortical neurons.
• To determine how neuronal stimulation affects CTCF and cohesin occupancy and its link to transcriptional changes.

Main Methods:

• Compared occupancy of CTCF, SMC1, RAD21, and RNAPII in cultured mouse cortical neurons.
• Analyzed changes in protein occupancy upon neuronal stimulation.
• Investigated the role of topoisomerases and DNA supercoiling in regulating cohesin binding.

Main Results:

• CTCF and cohesin are enriched at transcription start sites (TSS) and their levels correlate with RNAPII occupancy.
• Neuronal stimulation led to a rapid, genome-wide decrease in SMC1 and RAD21 signals at TSS, loop anchors, and TAD boundaries.
• Cohesin loss was independent of CTCF but mimicked by topoisomerase inhibition, and correlated with increased DNA supercoiling.

Conclusions:

• RNAPII may facilitate CTCF and cohesin binding to chromatin.
• Neuronal activity triggers cohesin dissociation from chromatin, mediated by increased DNA torsional stress.
• Modulation of torsional stress is a potential mechanism for regulating cohesin engagement and chromatin architecture in neurons.