Biology subjects

Hossain, F.

Publications and source records attributed to Hossain, F..

6 recordsLinked to original sources

bioRxiv2026

Small Structural Variations, Large Functional Consequences: Comparative Analysis Reveals Structural Control of Ubiquitylation Site Selection by BRCA1/BARD1

BRCA1/BARD1 is a chromatin-associated E3 ubiquitin ligase that ubiquitylates histone H2A to coordinate DNA damage repair, transcriptional repression, and genome stability. In Caenorhabditis elegans (C. elegans), the orthologous BRC-1/BRD-1 com-plex performs analogous functions but exhibits structural variation, most notably through an additional 11-residue loop in BRD-1 that is absent from human BARD1. Prior exper-iments indicate this worm-specific insertion promotes nucleosome engagement and may alter the preferred lysine target for ubiquitylation. Here, we provide a cross-species comparison by integrating computational and experimental investigation to clarify how a discrete structural variation can tune BRCA1-family ligase behavior and, consequently, chromatin regulation. In vitro ubiquitylation assays and mass spectrometry reveal BRC-1/BRD-1 ubiquitylate the C-terminal tail of histone H2A with less specificity than the human homologs. All-atom molecular dynamics simulations of both the C. elegans BRC-1/BRD-1-LET-70-Ubiquitin assembly and the human BRCA1/BARD1-UbcH5c-Ubiquitin complex in the presence of the nucleosome core particle uncover that the BRD-1 loop makes transient contacts with nucleosomal DNA and histone tails, thereby modulating the positioning and conformational flexibility of the bound E2 (ubiquitin-conjugating enzyme). Together, our results suggest that the BRD-1 loop alters the E3-E2 geometry, thereby altering ubiquitylation-site specificity.

biophysics↗

bioRxiv2025

Generative Landscapes and Dynamics to Design Multidomain Artificial Transmembrane Transporters

Protein design is challenging as it requires simultaneous consideration of interconnected factors, such as fold, dynamics, and function. These evolutionary constraints are encoded in protein sequences and can be learned through the latent generative landscape (LGL) framework to predict functional sequences by leveraging evolutionary patterns, enabling exploration of uncharted sequence space. By simulating designed proteins through molecular dynamics (MD), we gain deeper insights into the interdependencies governing structure and dynamics. We present a synergized workflow combining LGL with MD and biochemical characterization, allowing us to explore the sequence space effectively. This approach has been applied to design and characterize two artificial multidomain ATP-driven transmembrane copper transporters, with native-like functionality. This integrative approach proved effective in unraveling the intricate relationships between sequence, structure, and function.

biophysics↗

bioRxiv2024

Bioorthogonal labeling and enrichment of histone monoaminylation reveal its accumulation and regulatory function in cancer cell chromatin

Histone monoaminylation (i.e., serotonylation and dopaminylation) is an emerging category of epigenetic mark occurring on the fifth glutamine (Q5) residue of H3 N-terminal tail, which plays significant roles in gene transcription. Current analysis of histone monoaminylation is mainly based on site-specific antibodies and mass spectrometry, which either lacks high resolution or is time-consuming. In this study, we report the development of chemical probes for bioorthogonal labeling and enrichment of histone serotonylation and dopaminylation. These probes were successfully applied for the monoaminylation analysis of in vitro biochemical assays, cells, and tissue samples. The enrichment of monoaminylated histones by the probes further confirmed the crosstalk between H3Q5 monoaminylation and H3K4 methylation. Finally, combining the ex vivo and in vitro analyses based on the developed probes, we have shown that both histone serotonylation and dopaminylation are highly enriched in tumor tissues that overexpress transglutaminase 2 (TGM2) and regulate the three-dimensional architecture of cellular chromatin. TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=154 SRC="FIGDIR/small/586010v3_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@1bee3f7org.highwire.dtl.DTLVardef@1687013org.highwire.dtl.DTLVardef@1960bd0org.highwire.dtl.DTLVardef@1e19a04_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2023

The efficacy of CB-103, a first-in-class transcriptional Notch inhibitor, in preclinical models of breast cancer

BackgroundNotch signaling has been shown to mediate treatment resistance and support cancer stem cells (CSCs) in endocrine-resistant estrogen receptor positive (ER+) and triple negative breast cancers (TNBCs). The clinical development of GSIs, first generation Notch inhibitors, has been hindered by lack of Notch specificity and dose-limiting toxicity. Here we describe the safety and efficacy of a first-in-class, clinical stage, orally available small molecule pan-Notch inhibitor, CB-103. Due to its unique mode of action, CB-103 doesnt induce GI toxicities noted with GSIs. There is a critical need for effective, safe, targeted therapies for patients with endocrine-refractory metastatic breast cancer. Recently approved targeted therapies for TNBC are only effective for a subset of patients. Moreover, GSI-resistant, constitutively activating Notch1 or Notch2 mutations are observed in [~]10% of TNBC. Our study elucidating the synergy of CB-103 with fulvestrant and paclitaxel in preclinical models of both hormone-refractory ER+ BC and TNBC respectively provides a novel and unique opportunity to address major unmet therapeutic needs. MethodsCB-103 was screened in combination with a panel of anti-neoplastic drugs. We evaluated the anti-tumor activity of CB-103 with fulvestrant in ESR1-mutant (Y537S), endocrine-resistant BC xenografts. In the same model, we examined anti-CSC activity in mammosphere formation assays for CB-103 alone or in combination with fulvestrant or palbociclib. We also evaluated the effect of CB-103 plus paclitaxel on primary tumors and CSC in GSI-resistant TNBC model HCC1187. Comparisons between groups were performed with two-sided unpaired Students t-test. One-way or two-way ANOVA followed by Tukeys post analysis was performed to analyze in vivo efficacy study results. ResultsCB-103 showed synergism with fulvestrant in ER+ cells and with paclitaxel in TNBC cells. CB-103 combined with fulvestrant or paclitaxel potently inhibited mammosphere formation in both models. Combination of CB-103 and fulvestrant significantly reduced tumor volume in an ESR1-mutant, endocrine-resistant BC model. In a GSI-resistant TNBC model, CB-103 plus paclitaxel significantly delayed tumor growth compared to paclitaxel alone. ConclusionsOur data indicate that CB-103 is an attractive candidate for clinical investigation in endocrine resistant, recurrent breast cancers with biomarker-confirmed Notch activity in combination with SERDs and/or CDKis and in TNBCs with biomarker-confirmed Notch activity in combination with taxane-containing chemotherapy regimens.

cancer biology↗

bioRxiv2022

Targeting Cblb-Notch1 axis as a novel immunotherapeutic strategy to boost CD8+ T-cells responses

A critical feature of cancer is the ability to induce immunosuppression and evade immune responses. Tumor-induced immunosuppression diminishes the efficacy of endogenous immune responses and decreases the efficacy of cancer immunotherapy. In this study, we describe a new immunosuppressive pathway in which adenosine promotes Cbl-b-mediated Notch1 degradation, causing suppression of CD8+ T-cells effector functions. Genetic KO and pharmacological inhibition of Cbl-b prevents Notch1 degradation in response to adenosine and reactivates its signaling. Reactivation of Notch1 results in enhanced CD8+ T-cell effector functions, anti-cancer response and resistance to immunosuppression. Our work demonstrates that targeting Cbl-b-Notch1 axis is a novel promising strategy for cancer immunotherapy.

cancer biology↗

bioRxiv2021

H2S Prodrug, SG-1002, Protects Against Myocardial Oxidative Damage and Hypertrophy via Induction of Cystathionine beta-Synthase and Antioxidant Proteins

Endogenously produced hydrogen sulfide (H2S) is critical for cardiovascular homeostasis. Therapeutic strategies aimed at increasing H2S levels have proven cardioprotective in models of acute myocardial infarction (MI) and heart failure (HF). The present study was undertaken to investigate the effects of a novel H2S prodrug, SG-1002, on stress induced hypertrophic signaling in murine HL-1 cardiac muscle cells. Treatment of HL-1 cells with SG-1002 under serum starvation without or with H2O2 increased the levels of H2S, H2S producing enzyme, cystathionine {beta}-synthase (CBS) as well as antioxidant protein levels, such as super oxide dismutase1 (SOD1) and catalase and decreased oxidative stress. SG-1002 also decreased the expression of hypertrophic/HF protein markers such as atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in stressed HL-1 cells. Treatment with SG-1002 caused a significant induction of cell viability and a marked reduction of cellular cytotoxicity in HL-1 cells under serum starvation incubated or with H2O2. Experimental results of this study suggest that SG-1002 attenuates myocardial cellular oxidative damage and/or hypertrophic signaling via increasing H2S levels or H2S producing enzyme, CBS and antioxidant proteins.

cell biology↗