Temporal autoregulation during human PU.1 locus SubTAD formation

Area of Science:

• Genomics and Epigenetics
• Molecular Biology
• Cancer Research

Background:

• Epigenetic gene regulation relies on the 3D organization of chromatin within topologically associating domains (TADs).
• The precise spatial requirements for gene regulation, especially in cancer, remain largely undefined.
• Understanding these spatial dynamics is critical for deciphering gene dysregulation in diseases like acute myeloid leukemia (AML).

Purpose of the Study:

• To investigate the 3D genome organization of the PU.1 gene locus in healthy monocytes and AML cells.
• To identify the specific genomic regions and regulatory elements involved in PU.1 gene expression control.
• To elucidate the role of PU.1 autoregulation and LDB1 in establishing and maintaining spatial chromatin interactions.

Main Methods:

• High-resolution chromosomal conformation capture sequencing (Hi-C) was employed.
• Mapping the 3D organization of the human PU.1 locus in both healthy and cancerous myeloid cells.
• Analysis of dynamic chromosomal interactions within a defined genomic unit.

Main Results:

• A dynamic ∼75-kb unit, termed a SubTAD, was identified as the key region for PU.1 gene regulatory element interactions.
• These spatial interactions are essential for myeloid differentiation but are disrupted in AML.
• PU.1 autoregulation initiates these interactions by recruiting LDB1, which subsequently stabilizes them independently.

Conclusions:

• PU.1 autoregulation acts in a "hit-and-run" mechanism to initiate stable chromosomal loops.
• These loops establish a transcriptionally active chromatin architecture necessary for myeloid gene expression.
• Disruption of this process in AML highlights a novel mechanism of gene dysregulation in cancer.