A far downstream enhancer for murine Bcl11b controls its T-cell specific expression.

Area of Science:

• Hematopoiesis
• Molecular Biology
• Gene Regulation

Background:

• Bcl11b is a T-cell specific gene essential for T-lineage commitment.
• Aberrant BCL11B expression is implicated in human T-cell acute lymphoblastic leukemia (T-ALL).

Purpose of the Study:

• To elucidate the regulatory mechanisms controlling Bcl11b's distinctive T-lineage expression.
• To identify cis-regulatory elements responsible for Bcl11b's cell-type-specific expression.

Main Methods:

• Correction of the Bcl11b transcription start site.
• Mapping of a cell-type-specific differentially methylated region.
• Chromatin conformation capture (3C) assays to study looping interactions.
• Reporter assays and functional dissection of cis-regulatory elements.
• Analysis using bacterial artificial chromosome (BAC) constructs.

Main Results:

• A novel cis-regulatory element, the 'Major Peak,' located 850 kb downstream of Bcl11b, was identified.
• The Major Peak exhibits dynamic histone marking patterns mirroring the Bcl11b promoter.
• Long-range looping interactions between promoter-proximal elements and the Major Peak are essential for T-cell specific Bcl11b expression.
• Specific subregions within the Major Peak, including TCF-1 binding sites, are critical for T-lineage activation and silencing in non-T cells.
• T-cell specific expression of Bcl11b requires both promoter-proximal elements and the distant Major Peak.

Conclusions:

• Bcl11b expression is controlled by a complex regulatory network involving long-range cis-regulatory elements.
• The Major Peak acts as a crucial enhancer element, interacting with the Bcl11b promoter over a distance of 850 kb.
• Understanding these regulatory mechanisms is vital for comprehending T-cell development and T-ALL pathogenesis.