Nucleolar Stress Functions Upstream to Stimulate Expression of Autophagy Regulators

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Research

Background:

• Ribosome biogenesis is crucial for cell function and occurs in nucleoli.
• Disrupting ribosome biogenesis triggers nucleolar stress, leading to cell cycle arrest or apoptosis.
• Nucleolar stress is implicated in cancer and can activate compensatory pathways like autophagy.

Purpose of the Study:

• To investigate the mechanisms by which nucleolar stress influences autophagy.
• To determine if nucleolar stress affects the expression of key autophagic regulators.
• To explore the connection between ribosome biogenesis, nucleolar stress, and autophagy in cancer cells.

Main Methods:

• Induction of nucleolar stress via knockdown of ribosome biogenesis factors (SBDS, PPAN, NPM, PES1) or RNA polymerase I inhibition (CX-5461, UBF-1 depletion).
• Analysis of autophagic regulator expression (ATG7, ATG16L1) using molecular biology techniques.
• Assessment of autophagic flux in response to RNA polymerase I inhibition.

Main Results:

• Nucleolar stress induced by SBDS or ribosome biogenesis factor knockdown enhances ATG7 levels in cancer cells.
• Interference with RNA polymerase I function (CX-5461, UBF-1 depletion) also increases ATG7 expression.
• Pharmacological inhibition of RNA polymerase I with CX-5461 stimulates autophagic flux.

Conclusions:

• Nucleolar stress transcriptionally regulates autophagy, impacting key regulators like ATG7.
• The study establishes a link between nucleolar stress and autophagy.
• This connection presents a potential therapeutic target for cancer treatment.