Hypoxia-inducible C-to-U coding RNA editing downregulates SDHB in monocytes

Area of Science:

• Molecular Biology
• Epigenetics
• Cell Biology

Background:

• RNA editing is a post-transcriptional process altering gene coding sequences.
• Succinate dehydrogenase subunit B (SDHB) mRNA undergoes C-to-U editing, inactivating a fraction of transcripts.
• SDHB is a tumor suppressor complex implicated in paraganglioma and hypoxia-inducible pathways.

Purpose of the Study:

• To investigate the regulation, extent, and cellular origin of SDHB RNA editing.
• To understand the role of SDHB RNA editing in response to physiological stimuli.
• To explore the potential link between SDHB RNA editing and hypoxia adaptation.

Main Methods:

• Utilized short-term cultured peripheral blood mononuclear cells (PBMCs) from healthy donors.
• Employed allele-specific quantitative PCR, flow cytometry, and cell sorting for cell type analysis.
• Conducted gene expression microarray and high-throughput RNA sequencing.
• Analyzed large-scale RNA sequence datasets from human tissues and cell types (Illumina Body Map, ENCODE).

Main Results:

• SDHB RNA editing rate is low in uncultured monocytes but significantly upregulated under hypoxia (1% oxygen) and during normoxic macrophage differentiation.
• CD14-positive monocytes showed significantly higher editing rates compared to CD14-negative lymphocytes.
• Analysis of large datasets confirmed site-specific C136U editing in whole blood and CD14+ monocytes, with minimal editing in other cell types.
• Genomic DNA for SDHB remained wild-type, indicating RNA-level regulation.

Conclusions:

• SDHB C-to-U coding RNA editing is dynamically induced by physiological factors like hypoxia and differentiation.
• Site-specific RNA editing of SDHB in monocytes suggests a role in epigenetic downregulation and hypoxia adaptation.
• This study highlights RNA editing as a regulatory mechanism in immune cell responses to environmental changes.