Multiple E2F-induced microRNAs prevent replicative stress in response to mitogenic signaling

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• MicroRNA (miRNA) transcription regulation is not fully understood, especially during the cell division cycle.
• Protein-coding gene regulation models are often applied to miRNA transcription.
• The role of miRNAs in cell cycle progression requires further investigation.

Purpose of the Study:

• To investigate the regulation of miRNA transcription during the cell cycle.
• To identify specific miRNAs and transcription factors involved in cell cycle control.
• To understand the functional impact of E2F-regulated miRNAs on cell proliferation.

Main Methods:

• Analysis of miRNA transcription profiles in primary fibroblasts upon mitogenic stimulation.
• Investigation of miRNA induction by E2F1 and E2F3 during the G(1)/S transition.
• Assessment of miRNA regulation in E2F1/3-knockout cells.
• Identification of direct miRNA cluster targets of E2F1 and E2F3.

Main Results:

• Approximately 33% of expressed miRNAs are induced upon exit from quiescence.
• Many induced miRNAs are E2F1/E2F3 targets during G(1)/S transition and repressed in knockout cells.
• Specific miRNA clusters (let-7a-d, let-7i, mir-15b-16-2, mir-106b-25) are direct E2F targets.
• E2F-induced miRNAs inhibit, rather than promote, G(1)/S transition by targeting cell cycle regulators.
• Absence of these miRNAs leads to increased S-phase entry and DNA damage.

Conclusions:

• E2F transcription factors regulate specific miRNAs during the G(1)/S transition.
• E2F-induced miRNAs act as negative feedback regulators, limiting cellular responses to E2F activation.
• These miRNAs prevent replicative stress and DNA damage, playing a crucial role in cell cycle control.
• E2F-mediated control of miRNAs has implications for cell proliferation and diseases like cancer.