Journal Article

Pro-Oncogenic Transcription Factors BACH1 and Nrf2 Associate with Cytoplasmic Biomolecular Condensates of GFP-MxA (Myxovirus Resistance Protein A) in Oral Cancer Cells

Yuan, Huijuan, Sehgal, Pravin B.

2026

Overview

Biomolecular condensates in the cytoplasm and nucleus contribute to carcinogenesis through aberrant signaling by assorted transcription factors and fusion oncoproteins. Oral cancer, which is highly prevalent worldwide, frequently occurs in a U-shaped “high-risk” zone (floor of mouth, side of tongue, and anterior fauces) which forms the path of liquid transit through the mouth. We previously reported that environmental stresses of saliva-like hypotonicity and beverage-like temperature changes triggered cycles of disassembly/reassembly of biomolecular condensates of GFP-tagged human myxovirus resistance protein (MxA; alias Mx1) in oral cancer cells. In the present study, we identified some of the constituents of GFP-MxA cytoplasmic condensates in oral cells. These condensates were isolated from interferon (IFN)-λ1-treated GFP-MxA expressing OECM1 human oral cancer cells using magnetic bead-based immunoisolation. Unbiased peptide identification confirmed the presence of MxA/Mx1 peptides; however, the strongest intensity was for the BACH1 transcription factor family. Immunofluorescence analyses confirmed the association of BACH1 and the family member Nrf2 with cytoplasmic human GFP-MxA condensates. Moreover, GFP-BACH1 and GFP-Nrf2 colocalized with cytoplasmic human HA-MxA condensates in transiently transfected OECM1 cells. Western blot assays confirmed the presence of BACH1 and Nrf2 proteins in complexes isolated using anti-MxA pAb. As much as BACH1 and Nrf2 regulate oxidative stress response genes, it was remarkable that immunofluorescence assays revealed the presence of heme oxygenase 1 (HO1)—a downstream redox regulator—in GFP-MxA condensates. However, these condensates were devoid of p62, KEAP1 and Cul3. In terms of aberrant function, in live cells, the Nrf2 transcription factor underwent rapid disassembly and reassembly cycles driven by saliva-like hypotonicity, and was also disassembled by sulforaphane. The data highlight the unexpected intersections in oral cells between MxA condensates and BACH1, Nrf2 and HO1—proteins well known to be involved in pathways regulating cellular responses to environmental and oxidative stresses, antiviral defense, oral epithelial dysplasia, and cancer progression and metastases.

• Publisher: MDPI AG,Multidisciplinary Digital Publishing Institute (MDPI)
• Subject: anatomical sites of oral cancer / BACH1 / Basic-Leucine Zipper Transcription Factors - metabolism / Biological response modifiers / Biology / biomolecular condensates / Biomolecular Condensates - metabolism / Cancer / Cancer cells / Carcinogenesis / Cell Line, Tumor / Cellular stress response / Condensates / Cytoplasm / Cytoplasm - metabolism / DNA binding proteins / environmental stresses and carcinogens / Ethylenediaminetetraacetic acid / Green Fluorescent Proteins - metabolism / Heme / Heme oxygenase (decyclizing) / human myxovirus resistance protein (MxA/Mx1) / Humans / Hypotheses / Hypotonicity / Immunofluorescence / Interferon / Localization / Metastases / Mouth / Mouth cancer / Mouth Neoplasms - metabolism / Mouth Neoplasms - pathology / Myxovirus resistance proteins / Myxovirus Resistance Proteins - metabolism / NF-E2-Related Factor 2 - metabolism / Oncology, Experimental / Oral cancer / Oral carcinoma / Oxidative stress / Pathogenesis / pathogenesis of oral cancer / Peptides / Proteins / Proteomics / Saliva / Spectrum analysis / Sulforaphane / Transcription factors / Tumorigenesis / Viruses