Sequential RNA polymerase II activation drives human hematopoiesis

Area of Science:

• Cell Biology
• Developmental Biology
• Immunology

Background:

• Promoter-proximal pausing of RNA polymerase II (Pol II) is crucial for rapid gene activation.
• The temporal dynamics of Pol II in adult stem cells for environmental response remain unclear.

Purpose of the Study:

• To investigate the temporal organization of Pol II dynamics in adult stem cells.
• To understand how Pol II regulation enables flexible responses to environmental cues, specifically inflammatory stress.

Main Methods:

• Developed sciCUT&Tag2in1 for simultaneous single-cell profiling of Pol II and histone modifications.
• Applied the method to over 200,000 CD34+ hematopoietic stem cells (HSCs) and progenitors.

Main Results:

• Identified a Pol II regulatory cascade orchestrating the response to granulocyte colony-stimulating factor (G-CSF).
• Observed elevated Pol II occupancy and reduced Polycomb repression in activated HSCs for immune genes.
• Described sequential modes of Pol II activation during lineage commitment, involving pause-and-release and initiate-and-release genes.

Conclusions:

• sciCUT&Tag2in1 provides a tool to define the temporal logic of paused Pol II in adult stem cells.
• Demonstrated how paused Pol II enables flexible lineage decisions during development and in response to inflammation.
• Highlighted the role of Pol II dynamics in the intersection of development, inflammation, and disease.