Biology subjects

Paz, S.

Publications and source records attributed to Paz, S..

5 recordsLinked to original sources

bioRxiv2026

SRSF1 coordinates transcription and alternative splicing to modulate p53 and genome-maintenance

Serine/arginine-rich splicing factor 1 (SRSF1) regulates alternative splicing and acts as a proto-oncogene, but its role in transcription remains poorly defined. We combined time-course RNA-seq with experimental validation to define SRSF1-dependent transcriptional and splicing programs. We validated 67 of 143 alternative-splicing events selected for experimental analysis. Among these, 44 were not annotated in GENCODE, including 15 containing previously unannotated exons. Thirty-five events showed concordant regulation in HEK293 and breast and prostate cancer cell lines, and 17 events in 16 genes affected p53 regulation or p53-dependent functions. SRSF1 overexpression reduced total p53, increased basal Ser15 phosphorylation, and increased apoptosis under basal and cisplatin-treated conditions but not following doxorubicin treatment. SRSF1 also increased transcription of 28 genes, 18 of which showed concordant regulation across the same cellular models. Mechanistic studies linked SRSF1-dependent transcriptional activation to P-TEFb mobilization from the 7SK snRNP, which controls P-TEFb availability for RNA polymerase II elongation. These findings identify distinct but concurrent SRSF1-regulated programs: transcriptional activation of genes associated with cellular signaling and organization and alternative splicing modulating genome-maintenance and p53-regulatory genes.

molecular biology↗

bioRxiv2026

Repeated SARS-CoV-2 Antigenic Exposures from Prior Vaccinations and Infections Demonstrate Limits of Antibody Durability and Breadth Against Newer Variants

BackgroundWidespread immunity from vaccination and infection has reduced COVID-19 morbidity and mortality, but this immunity varies across the population. Understanding how repeated antigenic exposures influence antibody responses helps to inform future vaccination strategies. MethodsSerum samples collected one and six months after XBB.1.5 vaccination from 25 generally healthy healthcare workers with varying exposure histories were assessed for neutralizing activity against a range of variants, from pre-Omicron variants to latest Omicron JN.1 sublineage variants and divergent BA.3.2 variants, using lentiviral pseudoviruses. Participants were stratified by vaccination and infection history. ResultsXBB.1.5 vaccination elicited broad neutralizing responses, with strong boosting against previously encountered antigens relative to vaccine-matched XBB.1.5 and newer variants. Geometric mean neutralization titers were generally comparable across exposure groups, indicating limited influence of prior Omicron infection or bivalent vaccination, though intra-group heterogeneity was observed. At six months, overall titers declined by 36-62%. Titers remained highest against the pre-Omicron and lowest against JN.1 sublineage variants. N-terminal glycosylation (DelS31, T22N) modestly affected neutralization. ConclusionsXBB.1.5 vaccination elicited broad neutralizing antibody responses against previously encountered and vaccine-matched antigens regardless of exposure history, but titers waned after six months. This waning, compounded by continued emergence of immune-evasive variants and heterogenous population immunity, underscores the need for continually monitoring neutralizing antibody durability and breadth to guide evidence-based COVID-19 vaccine formulation updates.

microbiology↗

bioRxiv2024

Antigenic cartography using hamster sera identifies SARS-CoV-2 JN.1 evasion seen in human XBB.1.5 booster sera

Antigenic assessments of SARS-CoV-2 variants inform decisions to update COVID-19 vaccines. Primary infection sera are often used for assessments, but such sera are rare due to population immunity from SARS-CoV-2 infections and COVID-19 vaccinations. Here, we show that neutralization titers and breadth of matched human and hamster pre-Omicron variant primary infection sera correlate well and generate similar antigenic maps. The hamster antigenic map shows modest antigenic drift among XBB sub-lineage variants, with JN.1 and BA.4/BA.5 variants within the XBB cluster, but with five to six-fold antigenic differences between these variants and XBB.1.5. Compared to sera following only ancestral or bivalent COVID-19 vaccinations, or with post-vaccination infections, XBB.1.5 booster sera had the broadest neutralization against XBB sub-lineage variants, although a five-fold titer difference was still observed between JN.1 and XBB.1.5 variants. These findings suggest that antibody coverage of antigenically divergent JN.1 could be improved with a matched vaccine antigen.

microbiology↗

bioRxiv2021

Mechanism Driven Early Stage Identification and Avoidance of Antisense Oligonucleotides Causing TRL9 Mediated Inflammatory Responses in Bjab cells

Nucleic acid-based PS-ASOs have the potential to activate cellular innate immune responses, and the level of activation can vary quite dramatically with sequence. Minimizing degree of proinflammatory effect is one of the main selection criteria for compounds intended to move into clinical trials. While a recently developed hPBMC-based assay showed excellent ability to detect innate immune active PS-ASOs, which can then be discarded from the developmental process, this assay is highly resource-intensive and easily affected by subject variability. This compelled us to develop of a more convenient high-throughput assay. Here, we describe a new in vitro assay, utilizing a cultured human Bjab cell line, which was developed and validated to identify PS-ASOs that may cause innate immune activation. The assay was calibrated to replicate results from the hPMBC assay. The Bjab assay was designed to be high throughput and more convenient by using RT-qPCR readout of mRNA of the chemokine Ccl22. The Bjab assay was also shown to be highly reproducible and to provide a large dynamic range in determining the immune potential of PS-ASOs via comparison to known benchmark PS-ASO controls that were previously shown to be either safe or inflammatory in clinical trials. In addition, we demonstrate that Bjab cells can be used to provide mechanistic information on PS-ASO-TLR9 dependent innate immune activation.

pharmacology and toxicology↗

bioRxiv2021

Early-Stage Identification and Avoidance of Antisense Oligonucleotides Causing Species-Specific Inflammatory Responses in Human Volunteers Peripheral Blood Mononuclear Cells

A human peripheral blood mononuclear cell (PBMC)-based assay was developed to identify antisense oligonucleotide (ASO) with the potential to activate a cellular innate immune response outside of an acceptable level. The development of this assay was initiated when ISIS 353512 targeting the mRNA for human C-reactive protein was tested in a phase I clinical trial in which healthy human volunteers unexpectedly experienced increases in interleukin-6 (IL-6) and C-reactive protein. This level of immune stimulation was not anticipated following rodent and non-human primate safety studies in which no evidence of exaggerated proinflammatory effects were observed. The IL-6 increase induced by ISIS 353512 was caused by activation of B-cells. The IL-6 induction was inhibited by chloroquine pretreatment of the PBMC and the nature of the ASOs suggested that the response is mediated by a toll like receptor, in all likelihood TLR9. While assessing the inter PBMC donor variability, two class of responders to ISIS 353512 were identified (discriminator and non-discriminators). The discriminator source of PBMC was shown to produce low level of IL-6 after 24 hours in culture in absence of ASO treatment. The PBMC assay using discriminator donors was shown to be reproducible allowing to assess reliably the immune potential of ASOs via comparison to known benchmark ASO controls that were previously shown to be either safe or inflammatory in clinical trials.

pharmacology and toxicology↗