Kelenis, D. P. | bioRxiv Science

bioRxiv2025

A proteome-wide, MS-based screen identifies SUMOylation of host RNA splicing factors induced by HIV-1 infection

HIV-1 exploits host cell post-translation modifications (PTMs) to facilitate production of infectious particles. These modifications include SUMOylation, a dynamically regulated PTM involving covalent attachment of small ubiquitin-like modifiers (SUMOs) to lysine (K) residues of target proteins. SUMOylation modulates the activity of thousands of proteins and multiple fundamental host cellular processes, including pathways hijacked by HIV-1 to promote infection and spread. The SUMOylation of several proteins during HIV-1 infection has been characterized. However, the broad effects of HIV-1 infection on the SUMOylation of the host cell proteome is largely unknown. To date, SUMOylation has not been explored by large-scale proteomics in the context of HIV infection, where many SUMO-regulated host dependency factors remain to be identified. In this study, we performed a proteome-wide, mass spectrometry (MS)-based screen to identify proteins that are SUMOylated during HIV-1 infection. Here, and in biochemical assays, infection with HIV-1 led to the widespread increased SUMOylation of the heterogeneous nuclear ribonucleoprotein (HNRNP) A/B proteins, a protein family central to the regulation of alternative splicing. Intriguingly, this phenotype was found to be driven by expression of the HIV-1 Viral Infectivity Factor (Vif), suggesting a novel function for this protein aside from APOBEC3G degradation. We selected HNRNPA2B1 (A2/B1) and HNRNPA3 for further study, where depletion of these proteins led to the altered splicing of HIV-1 viral RNAs and dramatically reduced HIV-1 infectivity. Considering the enrichment of SUMOylation sites within the RNA-binding domains of the HNRNPA/B family, our data suggest a novel mechanism involving HIV-1-induced, Vif-mediated SUMOylation of host RNA splicing factors as a means to regulate HIV-1 alternative splicing. Broadly, our findings suggest that infection with HIV-1 alters the SUMOylation of many unexplored host cellular proteins, and provides a significant proteomic resource for their future mechanistic study.

molecular biology↗

bioRxiv2020

Lineage transcription factors co-regulate subtype-specific genes providing a roadmap for systematic identification of small cell lung cancer vulnerabilities

Lineage-defining transcription factors (LTFs) play key roles in tumor cell growth, making them highly attractive, but currently "undruggable", small cell lung cancer (SCLC) vulnerabilities. Delineating LTF genomic binding sites and associated chromatin features would provide important insights into SCLC dependencies. Here we map super-enhancers (SEs) across multiple patient-derived SCLC preclinical models, and find SE patterns are sufficient to classify the models into the recently defined, LTF-based, SCLC subtypes. 3D-chromatin conformation analysis identified genes associated with SEs that define subtype-specific tumor signatures with genes functioning in diverse processes. Focusing on ASCL1-high SCLC (SCLC-A), we found ASCL1 physically interacts with NKX2-1 and PROX1. These factors bind overlapping genomic regions, and co-regulate a set of genes, including genes encoding cell surface proteins, SCN3A and KCNB2 enriched in SCLC-A. Genetic depletion of NKX2-1 or PROX1 alone, or in combinations with ASCL1, did not inhibit SCLC growth more than that achieved by depleting ASCL1 alone. We demonstrate the SE signature supports the LTF classification of SCLC, identify NKX2-1 and PROX1 as ASCL1 co-factors, and substantiate the central importance of ASCL1 as a key dependency factor in the majority of SCLC. The LTF and SE gene sets provide a molecular roadmap for future ASCL1 therapeutic targeting studies.

cancer biology↗