Biology subjects

Singh, J. K.

Publications and source records attributed to Singh, J. K..

5 recordsLinked to original sources

bioRxiv2025

THE NSL COMPLEX PROMOTES NEURAL DEVELOPMENT BY PREVENTING R-LOOP INDUCED REPLICATION STRESS

Early neuronal development relies on the proliferation of neural progenitor cells, making this developmental stage particularly vulnerable to DNA replication impediments. Here, we identify a non-canonical role for the non-specific lethal (NSL) complex in safeguarding DNA replication during neurodevelopment. The NSL complex, which acetylates histone 4 at gene promoters and is mutated in Koolen-de Vries syndrome (KdVS), prevents unscheduled R-loop accumulation at weakly transcribed promoters that are typically devoid of R-loops. Single-cell sequencing reveals that loss of NSL causes replisome stalling and delayed S-phase progression. Neural organoids derived from KdVS patients exhibit impaired DNA replication, developmental abnormalities, and reduced synapse formation, driven entirely by unscheduled R-loop accumulation. These findings reveal that faithful DNA replication is critical for early neurodevelopment.

genomics↗

bioRxiv2024

Comparative Analysis of Lipid Nanoparticles in Pfizer-BioNTech and Moderna COVID-19 Vaccines: Insights from Molecular Dynamics Simulations

COVID-19 vaccines, such as Pfizer-BioNTechs BNT162b and Modernas mRNA-1273, have demonstrated robust efficacy. However, direct comparisons of their delivery vehicles remain limited. Notably, BNT162b requires storage at -80{degrees}C, while mRNA-1273 is stored at -20{degrees}C. This discrepancy in storage temperatures may be influenced by differences in the structure and stability of the lipid nanoparticles (LNPs) used in these vaccines. Ionizable lipids, such as SM-102 in Modernas vaccine and ALC-0315 in Pfizers vaccine, play a crucial role in LNP stability and function, affecting endosomal escape, cellular uptake, and drug release. Understanding these variations is essential for optimizing vaccine delivery systems. In our study, we use molecular dynamics simulations with the coarse-grained Martini forcefield to compare the LNPs in Moderna and Pfizers COVID-19 vaccines, providing insights at an experimental scale. Our findings indicate that the ionizable lipid tail of BNT162b (ALC-0315) exhibits a higher degree of branching, resulting in a more bifurcated appearance compared to the structure of the ionizable lipids in mRNA-1273 (SM-102).

biophysics↗

bioRxiv2024

In Silico Engineering of Stable siRNA Lipid Nanoparticles: Exploring the Impact of Ionizable Lipid Concentrations for Enhanced Formulation Stability

Lipid nanoparticles (LNPs) are crucial in advancing the delivery of RNA-based therapeutics within the domain of gene therapy. A comprehensive understanding of their formation and stability is critical for optimizing the clinical efficacy of LNPs. This study systematically investigates the influence of concentration variations of positive and neutral ionizable lipids - specifically, 2-[2,2-bis[(9Z,12Z)-octadeca-9,12-dienyl]-1,3-dioxolan-4-yl]-N,N-dimethylethanamine (DLinKC2-DMA) and 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) - along with cholesterol and polyethylene glycol, on the formation of LNPs and encapsulation of small interfering RNA (siRNA). Utilizing coarse-grained classical molecular dynamics (MD) simulations with a system size matching experimental range (approximately 0.6 million beads), we conduct a comparative analysis and offer mechanistic insights into siRNA formulation within LNPs containing positive and neutral DLinKC2-DMA. We found that the LNPs with positive ionizable lipids encapsulate more than twice the siRNA compared to the LNPs with neutral ionizable lipids. In addition to the formation of LNPs, our study extends to the forces governing siRNA escape from LNPs, employing steered molecular dynamics simulations. The force experienced by siRNA to cross the LNP lipid layer containing positive ionizable lipids was 400kJ/mol/nm more than that of neutral ionizable lipids, suggesting the encapsulation is more favorable with positive ionisable lipids.

biophysics↗

bioRxiv2022

Development of a Novel Bruton's Tyrosine Kinase Inhibitor that exerts Anti-Cancer Activities Potentiates Response of Chemotherapeutic Agents In Multiple Myeloma Stem Cell-Like Cells

Despite recent improvements in multiple myeloma (MM) treatment, MM remains an incurable disease and most patients experience a relapse. The major reason for myeloma recurrence is the persistent stem cell-like population. It has been demonstrated that overexpression of Brutons tyrosine kinase (BTK) in MM stem cell-like cells is correlated with drug resistance and poor prognosis. We have developed a novel small BTK inhibitor, KS151, which is unique compared to other BTK inhibitors. Unlike ibrutinib, and the other BTK inhibitors such as acalabrutinib, orelabrutinib, and zanubrutinib that covalently bind to the C481 residue in the BTK kinase domain, KS151 can inhibit BTK activities without binding to C481. This feature of KS151 is important because C481 becomes mutated in many patients and causes drug resistance. We demonstrated that KS151 inhibits in vitro BTK kinase activities and is more potent than ibrutinib. Furthermore, by performing a semi-quantitative, sandwich-based array for 71-tyrosine kinase phosphorylation, we found that KS151 specifically inhibits BTK. Our western blotting data showed that KS151 inhibits BTK signaling pathways and is effective against bortezomib-resistant cells as well as MM stem cell-like cells. Moreover, KS151 potentiates the apoptotic response of bortezomib, lenalidomide, and panobinostat in both MM and stem cell-like cells. Interestingly, KS151 inhibits stemness markers and is efficient in inhibiting Nanog and Gli1 stemness markers even when MM cells were co-cultured with bone marrow stromal cells (BMSCs). Overall, our results show that we have developed a novel BTK inhibitor effective against the stem cell-like population, and potentiates the response of chemotherapeutic agents.

molecular biology↗

bioRxiv2018

Management of Hsp90-Dependent Protein Folding by Small Molecule Targeting the Aha1 Co-Chaperone

The core cytosolic Hsp90 chaperone/co-chaperone complex plays a critical role in proteostasis management of human health and disease. To identify novel compounds that alter the ability of the Hsp90 co-chaperone Aha1 to modulate the ATPase activity found in multiple folding diseases ranging from steroid hormone receptor (SHR) sensitive prostate cancer to tauopathies associated with neurodegenerative diseases, we employed a high throughput screening (HTS) assay to monitor selectively Aha1-stimulated Hsp90 (ASH) ATPase activity. The ASH assay identified SEW04784 (SEW), a small molecule that disrupts ASH activity without inhibiting the basal Hsp90 ATPase activity. NMR analysis reveals that SEW binds to the C-terminal domain of Aha1 to disrupt its asymmetric binding to Hsp90 leading to abrogation of its chaperoning activity of Hsp90. SEW exhibits therapeutic potential by blocking the transcriptional activity of prostate cancer (PCa) associated variants of the androgen receptor (AR) in a cell-based model of PCa. Additionally, SEW exhibits the ability to clear toxic, phosphorylated tau aggregated species associated with tauopathies. By not directly impacting the basal ATPase function of the abundant and ubiquitous Hsp90, SEW could provide a therapeutic approach for mitigation of client-specific proteostatic disease.

biochemistry↗