Loss of Lamin A leads to the nuclear translocation of AGO2 and compromised RNA interference

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Research

Background:

• RNA interference (RNAi) was traditionally viewed as a cytoplasmic process.
• Recent studies indicate nuclear localization of Argonaute (AGO) proteins, suggesting nuclear RNAi functions.
• The precise role and implications of nuclear RNAi remain incompletely understood.

Purpose of the Study:

• To investigate the impact of Lamin A levels on nuclear Argonaute 2 (AGO2) localization.
• To elucidate the mechanisms underlying nuclear RNAi regulation and its role in cancer cell proliferation.
• To identify novel interactors of AGO2 in the nucleus and their functional significance.

Main Methods:

• Utilized SHSY5Y neuroblastoma and A375 melanoma cell lines with reduced Lamin A levels.
• Performed Argonaute fPAR-CLIP (UV crosslinking followed by immunoprecipitation and sequencing) to map AGO2 binding sites.
• Employed mass spectrometry to identify nuclear AGO2 interactomes.
• Conducted FAM120A fPAR-CLIP to analyze its binding patterns and interaction with AGO2 targets.

Main Results:

• Reduced Lamin A levels induced significant nuclear translocation of AGO2 in both cell lines.
• Lamin A knockout (KO) in SHSY5Y cells led to altered cell morphology, increased proliferation, and elevated oncogenic microRNA expression.
• AGO2 fPAR-CLIP in Lamin A KO SHSY5Y cells showed diminished RNAi activity.
• Mass spectrometry identified FAM120A as a nuclear AGO2 interactor that competes for AGO2 targets, reducing RNAi efficiency.

Conclusions:

• Loss of Lamin A promotes nuclear AGO2 import, leading to impaired RNAi.
• FAM120A plays a crucial role in mediating this RNAi impairment by interfering with AGO2 target binding.
• The observed nuclear AGO2 translocation and RNAi suppression contribute to increased cancer cell proliferation through oncogenic microRNA upregulation.