Conserved regulation of p53 network dosage by microRNA-125b occurs through evolving miRNA-target gene pairs

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• MicroRNAs (miRNAs) are key regulators of gene expression networks.
• MiR-125b, similar to lin-4 in C. elegans, influences neural and hematopoietic stem cell homeostasis.
• MiR-125b exhibits context-dependent roles in apoptosis and proliferation, central to the p53 network.

Purpose of the Study:

• To identify novel p53 network genes directly regulated by miR-125b.
• To investigate the conservation of miR-125b's regulatory role in the p53 pathway across species.
• To understand how miR-125b influences stem cell homeostasis and oncogenesis through p53 network modulation.

Main Methods:

• Utilized gain- and loss-of-function screens in humans, mice, and zebrafish to identify miR-125b targets.
• Validated identified targets using luciferase assays and a novel miRNA pull-down assay.
• Analyzed conservation of miRNA-target interactions and network-level regulation.

Main Results:

• Identified and validated 20 novel miR-125b targets within the p53 network.
• These targets include regulators of both apoptosis (e.g., Bak1, Puma, Tp53) and cell-cycle progression (e.g., cyclin C, Cdc25c, Cdkn2c).
• While individual miRNA-target pairs showed limited conservation, miR-125b's regulation of the p53 pathway is conserved at the network level across species.

Conclusions:

• MiR-125b acts as a buffer and fine-tuner of p53 network activity.
• By modulating the levels of both proliferative and apoptotic regulators, miR-125b impacts tissue stem cell homeostasis.
• Dysregulation of miR-125b's fine-tuning of the p53 network has implications for oncogenesis.