The histone chaperone CAF-1 safeguards somatic cell identity

Area of Science:

• Epigenetics and Chromatin Biology
• Stem Cell Biology
• Cellular Reprogramming

Background:

• Somatic cell identity maintenance involves complex chromatin remodeling.
• Mechanisms preserving the somatic state during differentiation are not fully understood.

Purpose of the Study:

• To identify chromatin factors regulating somatic cell identity.
• To elucidate pathways safeguarding the somatic state during reprogramming.

Main Methods:

• Conducted two RNA interference (RNAi) screens targeting chromatin factors.
• Utilized transcription-factor-mediated reprogramming of mouse fibroblasts to induced pluripotent stem cells (iPS cells).
• Analyzed chromatin accessibility, heterochromatin domains, and gene expression.

Main Results:

• Chromatin assembly factor-1 (CAF-1) subunits (Chaf1a, Chaf1b) were key hits in screens.
• CAF-1 suppression significantly increased reprogramming efficiency and accelerated iPS cell formation.
• CAF-1 inhibition led to accessible chromatin, reduced heterochromatin, and enhanced pluripotency gene activation.
• CAF-1 suppression also improved direct conversion of B cells to macrophages and fibroblasts to neurons.

Conclusions:

• The histone chaperone CAF-1 is a novel regulator of somatic cell identity.
• CAF-1 modulation enhances transcription-factor-induced cell-fate transitions.
• Findings offer a strategy to modulate cellular plasticity for regenerative applications.