Nuclear localized FAM21 participates in NF-κB-dependent gene regulation in pancreatic cancer cells

Abstract

The pentameric WASH complex is best known for its role in regulating receptor trafficking from retromer-rich endosomal subdomains. FAM21 functions to stabilize the WASH complex through its N-terminal head domain and localizes it to endosomes by directly binding the retromer through its extended C-terminal tail. Herein, we used affinity purification combined with mass spectrometry to identify additional FAM21-interacting proteins. Surprisingly, multiple components of the NF-κB pathway were identified, including p50 and p65. We show that FAM21 interacts with these components and regulates NF-κB-dependent gene transcription at the level of p65 chromatin binding. We further demonstrate that FAM21 contains a functional monopartite nuclear localization signal sequence (NLS1) as well as a CRM1/Exportin1-dependent nuclear exporting signal (NES1), both of which work jointly with the N-terminal head domain and C-terminal retromer recruitment domain to regulate FAM21 cytosolic and nuclear subcellular localization. Lastly, our findings indicate that FAM21 depletion sensitizes pancreatic cancer cells to gemcitabine and 5-fluorouracil. Thus, FAM21 not only functions as an integral component of the cytoplasmic WASH complex, but also modulates NF-κB gene transcription in the nucleus.