Biology subjects

Kosti, A.

Publications and source records attributed to Kosti, A..

3 recordsLinked to original sources

bioRxiv2026

Muscleblind-like proteins dimerize by forming disulfide bonds to regulate alternative splicing and pathogenic RNA foci formation

Muscleblind-like (MBNL) RNA-binding proteins (RBPs) possess modular domains that mediate regulation of alternative splicing and RNA localization. Myotonic Dystrophy Type 1 is a CTG repeat expansion disorder where MBNL is sequestered into intranuclear RNA foci, impairing its function. Previous studies found that MBNL self-associates through its exon 7, but the nature of this interaction is not well understood. We identified a cysteine in MBNL1 exon 7 that enables dimerization through formation of an intermolecular disulfide bond. We likewise demonstrate that MBNL2 dimerizes by forming disulfide bonds between multiple cysteines in its carboxy-terminus. Nucleocytoplasmic fractionation revealed a greater proportion of MBNL1 dimer in the nucleus, suggesting a nuclear function for the MBNL1 dimer. We investigated a connection between MBNL1 dimerization and MBNL1-mediated regulation of alternative splicing. To accomplish this, we mutated the MBNL1 cysteine in question to alanine (C325A) and performed RNAseq. We uncovered novel splicing events sensitive to MBNL1 dimerization. We also found that MBNL1 C325A, when co-expressed with expanded CTG repeats, produces smaller, more numerous foci, suggesting a role for the MBNL1 dimer in maintaining foci integrity. These results provide insight into biological and pathological mechanisms of MBNL1 dimerization and suggest other RBPs might similarly dimerize to regulate function. GRAPHICAL ABSTRACT

molecular biology↗

bioRxiv2026

MicroRNA combinations function as synergistic network regulators of neuroblastoma differentiation

Differentiation-based therapies represent a promising strategy for the treatment of neuroblastoma; however, single-agent approaches frequently yield incomplete and transient responses due to the robustness of underlying gene regulatory networks. MicroRNAs (miRNAs) are endogenous regulators of gene expression that modulate entire gene programs rather than individual molecular targets, making them attractive candidates for network-level therapeutic intervention. While individual miRNAs have been investigated as therapeutic agents, the potential for synergistic interactions between miRNAs remains largely unexplored. Here, we developed a scalable high-content phenotypic screening platform to identify synergistic miRNA combinations that promote neuronal differentiation and growth arrest in neuroblastoma cells. Using SK-N-BE(2)-C cells and automated quantification of neurite outgrowth and confluence, we screened pairwise combinations of differentiation-associated miRNAs at submaximal doses. Candidate synergistic interactions were identified using the Highest Single Agent framework and subsequently validated by dose-response interaction modeling. We identified a robust synergistic interaction between miR-124-3p and miR-363-3p that exceeded zero-interaction potency expectations by approximately 20.9% and increased maximal differentiation-associated phenotypic response by 73% relative to single-miRNA treatments. Target gene and pathway enrichment analyses revealed that miR-124-3p and miR-363-3p regulate largely distinct but functionally complementary target gene sets. These complementary targets converged on neuronal differentiation and cell cycle control pathways, providing a mechanistic basis for their cooperative activity. Together, these findings establish miRNA combinations as programmable network regulators capable of inducing complex cellular phenotypes with greater efficacy than single agents. This work provides a conceptual and experimental framework for the rational discovery of synergistic miRNA therapeutics and suggests new avenues for differentiation-based treatment strategies in neuroblastoma and other diseases driven by dysregulated regulatory networks.

molecular biology↗

bioRxiv2024

SERBP1 interacts with PARP1 and is present in PARylation-dependent protein complexes regulating splicing, cell division, and ribosome biogenesis

RNA binding proteins (RBPs) containing intrinsically disordered regions (IDRs) are present in diverse molecular complexes where they function as dynamic regulators. Their characteristics promote liquid-liquid phase separation (LLPS) and the formation of membraneless organelles such as stress granules and nucleoli. IDR-RBPs are particularly relevant in the nervous system and their dysfunction is associated with neurodegenerative diseases and brain tumor development. Serpine1 mRNA-binding protein 1 (SERBP1) is a unique member of this group, being mostly disordered and lacking canonical RNA-binding domains. We defined SERBP1s interactome, uncovered novel roles in splicing, cell division and ribosomal biogenesis, and showed its participation in pathological stress granules and Tau aggregates in Alzheimers brains. SERBP1 preferentially interacts with other G-quadruplex (G4) binders, implicated in different stages of gene expression, suggesting that G4 binding is a critical component of SERBP1 function in different settings. Similarly, we identified important associations between SERBP1 and PARP1/polyADP-ribosylation (PARylation). SERBP1 interacts with PARP1 and its associated factors and influences PARylation. Moreover, protein complexes in which SERBP1 participates contain mostly PARylated proteins and PAR binders. Based on these results, we propose a feedback regulatory model in which SERBP1 influences PARP1 function and PARylation, while PARylation modulates SERBP1 functions and participation in regulatory complexes.

genomics↗