Cyclin D1 overexpression induces global transcriptional downregulation in lymphoid neoplasms

Area of Science:

• Molecular Biology
• Cancer Research
• Gene Regulation

Background:

• Cyclin D1 is an oncogene overexpressed in many cancers.
• It functions as both a cell cycle and transcriptional regulator.
• Its transcriptional role, especially in cancer, is not fully understood.

Purpose of the Study:

• To investigate the transcriptional role of cyclin D1 in lymphoid tumor cells with oncogenic overexpression.
• To explore the impact of cyclin D1 on gene expression and RNA polymerase II activity.
• To identify potential therapeutic strategies targeting cyclin D1's transcriptional function.

Main Methods:

• Assessed cyclin D1 binding to gene promoters using ChIP-seq.
• Measured gene expression levels and nascent transcription rates.
• Analyzed RNA polymerase II pausing using nascent transcription assays.
• Investigated interactions between cyclin D1 and the transcription machinery.
• Evaluated sensitivity to transcription inhibitors and synthetic lethality in lymphoma models.

Main Results:

• Cyclin D1 binds to promoters of actively transcribed genes, correlating with transcriptional output.
• Overexpression of cyclin D1 leads to global transcriptional downregulation.
• This downregulation is linked to reduced nascent transcription and increased RNA polymerase II pausing.
• Cyclin D1 interacts with the transcription machinery, impairing transcription.
• Cyclin D1 overexpression sensitizes cells to transcription inhibitors, showing synthetic lethality in mantle cell lymphoma.

Conclusions:

• Oncogenic cyclin D1 dysregulates global transcription by impairing RNA polymerase II pausing.
• This expands the known functions of cyclin D1 beyond cell cycle regulation.
• Targeting the transcriptional machinery presents a potential therapeutic strategy for cyclin D1-overexpressing tumors.