YY1 Binding to Regulatory Elements That Lack Enhancer Activity Promotes Locus Folding and Gene Activation

Area of Science:

• Genomics
• Molecular Biology
• Epigenetics

Background:

• Enhancer-promoter interactions are critical for gene regulation but the mechanisms establishing these connections are not fully understood.
• Cohesin-mediated loop extrusion is implicated but may not be the sole mechanism.
• The precise roles of specific DNA-binding proteins in genome organization are actively investigated.

Purpose of the Study:

• To identify novel regulatory elements involved in genome organization and enhancer-promoter interactions.
• To investigate the role of the transcription factor YY1 in establishing these interactions.
• To explore the function of elements lacking intrinsic enhancer activity in locus regulation.

Main Methods:

• Identification and characterization of regulatory elements within the mouse immunoglobulin lambda (Igλ) light chain locus.
• Functional analysis of a specific element (HSCλ1) using knock-out strategies targeting YY1 binding sites.
• Genome-wide analysis of YY1-bound elements in mouse embryonic stem cells.

Main Results:

• An element (HSCλ1) with regulatory potential but lacking intrinsic enhancer/promoter activity was identified.
• Disruption of the YY1 binding site in HSCλ1 significantly reduced Igλ transcription and altered enhancer/promoter interactions.
• Genome-wide analyses revealed numerous YY1-bound elements within CTCF/cohesin loop boundaries that lack intrinsic enhancer activity.

Conclusions:

• YY1-bound elements, even without intrinsic enhancer activity, play a fundamental role in locus folding.
• These elements are essential for facilitating enhancer-promoter interactions, contributing to gene regulation.
• The findings propose a new model for genome organization and gene regulation involving specific DNA-binding proteins.