G-quadruplexes Sequester Free Heme in Living Cells.

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• Heme is vital but toxic when free, necessitating tight regulation.
• G-quadruplexes bind heme in vitro, suggesting a potential in vivo sequestration role.
• Understanding heme regulation is crucial for cellular health and disease.

Purpose of the Study:

• To investigate if G-quadruplexes sequester heme in vivo.
• To determine if displacing heme from G-quadruplexes affects gene expression related to heme and iron homeostasis.
• To explore the therapeutic potential of targeting G-quadruplex-heme interactions.

Main Methods:

• Utilized in vitro assays to confirm heme binding to G-quadruplexes.
• Treated cultured human cells with PhenDC3, a G-quadruplex ligand.
• Analyzed changes in gene transcription, focusing on heme degradation and iron homeostasis pathways.

Main Results:

• PhenDC3 displaced G-quadruplex-bound heme in vitro.
• Treatment altered cellular transcription, upregulating genes involved in heme degradation and iron homeostasis.
• Observed a striking 30-fold induction of heme oxidase 1, a key heme degradation enzyme.

Conclusions:

• G-quadruplexes likely sequester heme in vivo, acting as a protective mechanism against free heme toxicity.
• Targeting G-quadruplex-heme interactions offers a novel strategy to modulate cellular heme levels.
• This mechanism highlights a new pathway for managing iron and heme homeostasis.