Biology subjects

Sokolowski, M.

Publications and source records attributed to Sokolowski, M..

5 recordsLinked to original sources

bioRxiv2026

Loss of cBAF Complex Confers Sorafenib Resistance in Liver Cancer

Sorafenib resistance limits the clinical benefit of first-line therapy in hepatocellular carcinoma (HCC), yet the epigenetic mechanisms underlying this resistance remain poorly understood. Using a chromatin-focused CRISPR/Cas9 dropout screen in HepG2 cells, we identified subunits of the canonical BAF (cBAF) complex -- ARID1A, ARID1B, and SMARCC1 -- as functional drivers of sorafenib resistance, while loss of the PBAF-specific subunit ARID2 had no effect, implicating cBAF specifically rather than SWI/SNF broadly. ARID1A and ARID1B mutations are associated with significantly worse overall survival in TCGA hepatocellular carcinoma cohorts. To define the underlying mechanism, we performed CUT&RUN profiling and RNA-seq in ARID1B-knockout HepG2 cells under sorafenib treatment. ARID1B loss triggered selective depletion of H3K4me3 and H3K27ac at 74 cBAF-dependent regulatory elements, 72% of which were directly occupied by ARID1B in wild-type cells. These sites were enriched for FOXA1 and HNF4 motifs, consistent with disruption of hepatocyte lineage regulatory chromatin. Direct profiling in HLF hepatocellular carcinoma cells confirmed that 179 FOXA1 binding sites were lost specifically under the combined perturbation of ARID1B loss and sorafenib treatment, with neither condition alone sufficient to drive this effect. Transcriptionally, ARID1B loss induced epithelial-mesenchymal transition programs and suppressed MYC targets, E2F targets, and mTORC1 signaling. These findings define a cBAF-FOXA1 regulatory axis that maintains hepatocyte lineage identity under kinase inhibitor stress, and whose disruption drives epigenetic reprogramming toward a mesenchymal drug-tolerant state. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=92 SRC="FIGDIR/small/731725v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@1ce2352org.highwire.dtl.DTLVardef@70f2f5org.highwire.dtl.DTLVardef@15ee96borg.highwire.dtl.DTLVardef@2e7edd_HPS_FORMAT_FIGEXP M_FIG C_FIG

Cancer Biology↗

bioRxiv2026

Arginine methylation of BAF155 regulates interactions with RNA processing machinery

Post-translational modifications (PTMs) of chromatin remodelers are abundant but functionally understudied. Here we investigate the role of asymmetric dimethylation of arginine 1064 (BAF155me2a) on the SWI/SNF core subunit BAF155, a mark deposited by CARM1/PRMT4 that has been linked to tumor progression but whose molecular function remains unclear. Using immunoprecipitation-mass spectrometry with a dimethyl-specific antibody, we found that R1064me2 selectively enhances BAF155 interactions with RNA processing factors, including the anti-termination protein SCAF4, splicing factors, and the transcription factor RFX5. CUT&RUN profiling showed that BAF155me2a, SCAF4, and RFX5 co-occupy promoter regions, and reciprocal immunoprecipitations confirmed that the SCAF4-BAF155 interaction depends on R1064 methylation. To test the functional consequences of this modification, we generated cells expressing either wild-type BAF155 or a methylation-deficient BAF155-R1064K mutant. Loss of methylation did not alter chromatin accessibility, BAF155 genomic occupancy, or SCAF4 recruitment. However, nascent transcription measured by TT-seq revealed a coordinated reduction in 5' sense transcripts and upstream antisense transcripts (PROMPTs) at BAF155-bound promoters, with a quantitatively larger decrease in PROMPTs at SCAF4 co-bound sites. The effect was restricted to the promoter-proximal region and resolved toward the gene end, consistent with a defect in productive elongation downstream of RNA polymerase II recruitment. These data support a model in which BAF155 dimethylation provides a co-transcriptional interface coupling SWI/SNF to RNA processing machinery, and identify regulation of nascent transcription as a non-canonical function of SWI/SNF PTMs.

genomics↗

bioRxiv2025

Menin-MLL1 complex cooperates with NF-Y to promote HCC survival

Identification of new therapeutic targets in hepatocellular carcinoma (HCC) remains critical. Chromatin regulating complexes are frequently mutated or aberrantly expressed in HCC, suggesting dysregulation of chromatin environments is a key feature driving liver cancer. To investigate whether the altered chromatin state in HCC cells could be targeted, we designed and utilized an epigenome-focused CRISPR library that targets genes involved in chromatin regulation. This focused approach allowed us to test multiple HCC cell lines in both 2D and 3D growth conditions, which revealed striking differences in the essentiality of genes involved in ubiquitination and multiple chromatin regulators vital for HCC cell survival in 2D but whose loss promoted growth in 3D. We found the core subunits of the menin-MLL1 complex among the strongest essential genes for HCC survival in all screens and thoroughly characterized the mechanism through which the menin-MLL1 complex promotes HCC cell growth. Inhibition of the menin-MLL1 interaction led to global changes in occupancy of the complex with concomitant decreases in H3K4me3 and expression of genes involved in PI3K/AKT/mTOR signaling pathway. Menin inhibition affected chromatin accessibility in HCC cells, revealing that increased chromatin accessibility at sites not bound by menin-MLL1 was associated with the recruitment of the pioneer transcription factor complex NF-Y. A CRISPR/Cas9 screen of chromatin regulators in the presence of menin inhibitor SNDX-5613 revealed a significantly increased cell death when combined with NFYB knockout. Together these data show that menin-MLL1 is necessary for HCC cell survival and cooperates with NF-Y to regulate oncogenic gene transcription.

cancer biology↗

bioRxiv2020

Intestinal progenitor P-bodies maintain stem cell identity by suppressing pro-differentiation factors.

The role of Processing bodies (P-bodies), key sites of post-transcriptional control, in adult stem cells remains poorly understood. Here, we report that adult Drosophila intestinal stem cells, but not surrounding differentiated cells such as absorptive Enterocytes (ECs), harbor P-bodies that contain Drosophila orthologs of mammalian P-body components DDX6, EDC3, EDC4 and LSM14A/B. A targeted RNAi screen in intestinal progenitor cells identified 39 previously known and 64 novel P-body regulators, including Patr-1, a gene necessary for P-body assembly. Loss of Patr-1-dependent P-bodies leads to a loss of stem cells that is associated with inappropriate translation and expression of EC-fate gene nubbin. Transcriptomic analysis of progenitor cells identifies a cadre of such weakly transcribed pro-differentiation transcripts that are elevated after P-body loss. Altogether, this study identifies a coordinated P-body dependent, translational and transcriptional repression program that maintains a defined set of in vivo stem cells in a state primed for differentiation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=198 HEIGHT=200 SRC="FIGDIR/small/175398v2_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@d57273org.highwire.dtl.DTLVardef@14d057aorg.highwire.dtl.DTLVardef@1a2c4a5org.highwire.dtl.DTLVardef@11c5ba3_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIDrosophila intestinal progenitor cells contain constitutive and ultrastructurally organized P-bodies. C_LIO_LIA P-body regulator Patr-1 is required for intestinal progenitor cell maintenance. C_LIO_LIEnterocyte (EC) genes such as nubbin are weakly transcribed but not translated in intestinal progenitors. C_LIO_LIP-bodies repress EC gene translation to promote stem cell maintenance. C_LI

cell biology↗

bioRxiv2020

SGK1 Signaling Promotes Glucose Metabolism and Survival in Extracellular Matrix Detached Cells

Loss of integrin-mediated attachment to extracellular matrix (ECM) proteins can trigger a variety of cellular changes that impact cell viability. Foremost among these is the activation of anoikis, caspase-mediated cell death induced by ECM-detachment. In addition to anoikis, loss of ECM-attachment causes profound alterations in cellular metabolism that can lead to anoikis-independent cell death. Here, we describe a surprising role for serum and glucocorticoid kinase-1 (SGK1) in the promotion of energy production when cells are detached. Our data demonstrate that SGK1 activation is necessary and sufficient for ATP generation during ECM-detachment and anchorage-independent growth. More specifically, SGK1 promotes a substantial elevation in glucose uptake due to elevated GLUT1 transcription. In addition, carbon flux into the pentose phosphate pathway (PPP) is necessary to accommodate elevated glucose uptake and PPP-mediated glyceraldehyde-3-phosphate (G3P) is necessary for ATP production. Thus, our data unmask SGK1 as master regulator of glucose metabolism and cell survival during ECM-detached conditions.

cell biology↗