Biology subjects

Gowda, H.

Publications and source records attributed to Gowda, H..

12 recordsLinked to original sources

bioRxiv2026

Preservation of full-length transcripts at ambient temperature using ensilication

Background. Evaluation of RNA preservation requires an understanding of how storage conditions affect recoverable transcriptome information. Long-read RNA sequencing enables comprehensive assessment of transcript representation, isoform composition, and support for annotated transcript structures. This approach was employed to investigate the protective capabilities of ensilication during ambient and elevated-temperature storage. Results. Pooled human total RNA was analyzed using PacBio Kinnex across six conditions, with two replicates per storage condition. Comparisons included frozen controls as well as ensilicated and unprotected RNA stored for seven days at room temperature or 40 {degrees}C. At matched input depth, with at least one qualifying sequence per transcript, ensilicated samples retained 88-89% of a fixed frozen-reference transcript set at room temperature and approximately 85% at 40 {degrees}C. In contrast, unprotected RNA retained 78-83% and 42-64%, respectively. Ensilicated samples exhibited smaller changes in isoform composition among evaluable genes. The retention advantage persisted when sequences were required to support a uniquely distinguishing complete intron chain and both annotated transcript boundaries. Retention estimates varied with detection criteria, and substantial limitations in annotated end-to-end coverage were observed even in frozen controls. Conclusion. Long-read RNA sequencing demonstrates that ensilication limits storage-associated loss and distortion of recoverable transcriptome-wide information in the tested RNA preparation. These findings indicate a protective effect during seven days of ambient and elevated-temperature storage.

molecular biology↗

bioRxiv2025

EPHA2-dependent Ephrin-B1 signaling supports self-renewal ability and recurrence of oral cancer

Eph-Ephrin pathway that drives a bidirectional signaling regulates a plethora of biological activities with its varied level of complexity. While the canonical trans-interaction of the ligand and receptor on neighboring cells initiates forward signaling that brings about biological activities, their cis-interaction on the same cell attenuates the forward signaling, modulating the biological effects. Yet, non-canonical cis-interactions with heterotypic surface proteins and kinases regulate certain biological effects. In cancer, the canonical signaling is believed to be tumor suppressive, while the ligand-independent non-canonical signaling drives tumor progression and poor prognosis. Self-renewal ability of cancer cells is a major underlying cause of recurrence and poor prognosis of cancer. Using SILAC-based proteomics, we identified Ephrin-B1 signaling as a crucial regulator of oral cancer self-renewal. Though Ephrin-B1 is known to regulate normal stem cells, its role in cancer remains underexplored. Our biochemical analyses show that Ephrin-B1 binds to a nonconventional receptor EPHA2, which is known to regulate cancer stem cells (CSCs), though the mechanism is less explored. Contrary to the belief that the cis-interaction of receptors and ligands is a means to block functional signaling, our immunoprecipitation, FRET facilitated photoswitching analysis, proximity ligation assay, and in vitro kinase assay provide evidence for the Ephrin-B1-EPHA2 cis-interaction leading to the phosphorylation of EphrinB1 at Y324/329 and Y317. Extreme limiting dilution assay in vitro and in vivo confirmed that this cis-interaction promotes CSC enrichment. Substantiating our in vitro results, mouse orthotopic models showed that Ephrin-B1/EPHA2 interaction regulates prognosis. The clinical relevance of the finding was validated using a TCGA data set and immunohistochemical analysis of tissue microarray using samples from oral cancer patients with recurrence in comparison to patients, who showed disease-free survival. Given that Ephrin-B interacts with EphB for normal stem cell homeostasis, this unconventional EPHA2/Ephrin-B1 cis-interaction, specifically manifested in CSC niches, might serve as an attractive target for therapy, warranting further validation.

cancer biology↗

bioRxiv2023

CRISPR-Cas13d screens identify KILR a breast cancer risk-associated lncRNA that regulates DNA replication and repair.

Long noncoding RNAs (lncRNAs) have surpassed the number of protein-coding genes, yet the majority have no known function. We previously discovered >800 lncRNAs at regions identified by breast cancer genome-wide association studies (GWAS). Here, we performed a pooled CRISPR-Cas13d RNA knockdown screen to identify which of these lncRNAs altered cell proliferation. We found that KILR, a lncRNA that functions as a tumor suppressor, safeguards breast cells against uncontrolled proliferation. The half-life of KILR is significantly reduced by the risk haplotype, revealing an alternative mechanism by which variants alter cancer risk. We showed that KILR sequesters RPA1, a subunit of the RPA complex, required for DNA replication and repair. Reduced KILR expression promotes cell proliferation by increasing the available pool of RPA1 and the speed of DNA replication. Our findings confirm lncRNAs as mediators of breast cancer risk, emphasize the need to annotate noncoding transcripts in relevant cell types when investigating GWAS variants and provide a scalable platform for mapping phenotypes associated with lncRNAs.

cancer biology↗

bioRxiv2023

Regulation of Non-Canonical Proteins Encoded by Small Open Reading Frames via the Nonsense-Mediated Decay Pathway.

Immunotherapy interventions relies heavily on neoantigen availability. The human genome encodes non-canonical/mutant proteins that potentially contain neoantigenic peptides. Nevertheless, their typically low expression, potentially moderated by the Nonsense-Mediated Decay (NMD) pathway, restricts their therapeutic utility. In this study, we explored the NMD pathway influence on non-canonical/mutant protein expression, specifically focusing on UPF1 knockdown. We implemented proteogenomic approaches to ascertain if the encoding transcripts and their respective proteins were upregulated post-knockdown. Complementary to this, we conducted a comprehensive pan-cancer survey of UPF1 expression and an in vivo evaluation of UPF1 expression in Triple-Negative Breast Cancer (TNBC) tissue. Our empirical results delineated that UPF1 knockdown precipitates an increase in the transcription of non-canonical/mutant proteins, especially those originating from retained-introns, pseudogenes, long non-coding RNAs, and unannotated biotypes. Furthermore, the analysis revealed that UPF1 expression was conspicuously high across a range of neoplastic tissues, with protein levels notably amplified in patient derived TNBC tumours in comparison to adjacent tissues. Our study elucidates UPF1 functional role in attenuating transcriptional noise through the degradation of transcripts encoding non-canonical/mutant proteins. Interestingly, we observed an upregulation of the NMD pathway in cancer, potentially functioning as a "neoantigen masking" mechanism that subdues non-canonical/mutant protein expression. Suppressing this mechanism may unveil a new cadre of neoantigens accessible to the antigen presentation pathway. Our novel findings proffer a solid base for devising therapeutic strategies targeting UPF1 or the NMD pathway, given the pronounced presence of UPF1 in malignant cells, thus potentially augmenting immunotherapeutic responses in cancer.

cell biology↗

bioRxiv2022

Codon optimality is the primary contributor to the exceptional mutational sensitivity of CcdA antitoxin in its operonic context

Deep mutational scanning studies suggest that synonymous mutations are typically silent and that most exposed, non active-site residues are tolerant to mutations. Here we show that the ccdA antitoxin component of the E.coli ccdAB toxin-antitoxin system is unusually sensitive to mutations when studied in the operonic context. A large fraction ([~]80%) of single-codon mutations, including many synonymous mutations in the ccdA gene shows inactive phenotype, but they retain native-like binding affinity towards cognate toxin, CcdB. Therefore, the observed phenotypic effects are largely not due to alterations in protein structure/stability, consistent with a large region of CcdA being intrinsically disordered. E. coli codon preference and strength of ribosome-binding associated with translation of downstream ccdB gene are found to be major contributors of the observed mutant phenotypes. In select cases, proteomics studies reveal altered ratios of CcdA:CcdB protein levels in vivo, suggesting that the ccdA mutations likely alter relative translation efficiencies of the two genes in the operon. We extend these results by studying single-site synonymous mutations that lead to loss of function phenotypes in the relBE operon upon introduction of rarer codons. Thus, in their operonic context, genes are likely to be more sensitive to both synonymous and non-synonymous point mutations than inferred previously.

molecular biology↗

bioRxiv2021

Low antigen abundance limits efficient T-cell recognition of highly conserved regions of SARS-CoV-2

Understanding the immune response to severe acute respiratory syndrome coronavirus (SARS-CoV-2) is critical to overcome the current coronavirus disease (COVID-19) pandemic. Efforts are being made to understand the potential cross-protective immunity of memory T cells, induced by prior encounters with seasonal coronaviruses, in providing protection against severe COVID-19. In this study we assessed T-cell responses directed against highly conserved regions of SARS-CoV-2. Epitope mapping revealed 16 CD8+ T-cell epitopes across the nucleocapsid (N), spike (S) and ORF3a proteins of SARS-CoV-2 and five CD8+ T-cell epitopes encoded within the highly conserved regions of the ORF1ab polyprotein of SARS-CoV-2. Comparative sequence analysis showed high conservation of SARS-CoV-2 ORF1ab T-cell epitopes in seasonal coronaviruses. Paradoxically, the immune responses directed against the conserved ORF1ab epitopes were infrequent and subdominant in both convalescent and unexposed participants. This subdominant immune response was consistent with a low abundance of ORF1ab encoded proteins in SARS-CoV-2 infected cells. Overall, these observations suggest that while cross-reactive CD8+ T cells likely exist in unexposed individuals, they are not common and therefore are unlikely to play a significant role in providing broad pre-existing immunity in the community.

immunology↗

bioRxiv2021

Deep learning-based pan-cancer classification model reveals cancer-specific gene expression signatures

The identification of cancer-specific biomarkers and therapeutic targets is one of the primary goals of cancer genomics. Thousands of cancer genomes, exomes, and transcriptomes have been sequenced to date. In this study, we conducted a pan-cancer analysis of transcriptome datasets from 37 cancer types provided by The Cancer Genome Atlas (TCGA) in an effort to identify cancer-specific gene expression signatures. We employed deep neural networks to train a model on the transcriptome profile datasets for all cancer types. The model was validated, and its predictive accuracy was determined using an independent dataset, achieving > 97% prediction accuracy across cancer types. This strongly suggests that there are distinct gene expression signatures associated with various cancer types. We interpreted the model using SHapley Additive exPlanations (SHAP) to identify specific gene signatures that significantly contributed to the classification of cancer types. In addition to known biomarkers, we identified several novel biomarkers in different cancer types. These cancer-specific gene signatures are valuable candidates for future studies of their potential utility as cancer biomarkers and putative therapeutic targets.

bioinformatics↗

bioRxiv2019

Marizomib suppresses triple-negative breast cancer via proteasome and oxidative phosphorylation inhibition

Lacking effective targeted therapies, triple-negative breast cancer (TNBCs) is highly aggressive with development of metastasis especially brain, and remains clinically challenging breast cancer subtype to treat. Despite the survival dependency on the proteasome pathway genes, FDA-approved proteasome inhibitors induced minimal clinical response in breast cancer patients due to weak proteasome inhibition. Here, we show that a potent proteasome inhibitor Marizomib (Mzb) inhibits multiple proteasome catalytic activities and induces a better anti-tumor response in TNBC cell lines and patient-derived xenografts alone and in combination with the standard-of-care chemotherapy. Mechanistically, Mzb inhibits oxidative phosphorylation (OXPHOS) via PGC-1 suppression in conjunction with proteasome inhibition in TNBC cells. Mzb reduces lung and brain metastases by reducing the number of circulating tumor cells and the expression of multiple genes involved in the epithelial-to-mesenchymal transition. Furthermore, Mzb-induced OXPHOS inhibition upregulates glycolysis to meet the energetic demands of TNBC cells and, hence, combined inhibition of glycolysis with Mzb exposure leads to a synergistic anti-cancer activity. Collectively, our data provide a strong rationale for a clinical evaluation of Mzb in primary and metastatic TNBC patients.\n\nOne Sentence SummaryMarizomib inhibits primary tumor growth, and also reduces lung and brain metastases in pre-clinical models of triple-negative breast cancer.

cancer biology↗

bioRxiv2019

Proteome-wide characterization and biomarker identification of intracranial aneurysm

The scientific basis of intracranial aneurysm (IA) formation, its rupture and further development of cerebral vasospasm remains incompletely understood. Deciphering the molecular mechanisms underlying these events will lead to identification of early detection biomarkers and in turn, improved treatment outcomes. Aberrant protein expression may drive structural alterations of vasculature found in IA. To unravel these aberrations, we performed untargeted, global, quantitative proteomic analysis of aneurysm tissue and serum from patients with IA. Samples were derived from patients of three clinical sub groups- 1) unruptured aneurysm 2) ruptured aneurysm without vasospasm 3) ruptured aneurysm who developed vasospasm. A total of 937 and 294 proteins were identified in aneurysm tissue and serum samples respectively. Several proteins that are known to maintain the structural integrity of vasculature were found to be dysregulated. ORM1, a glycoprotein, was significantly upregulated in both the aneurysm tissue and serum samples of unruptured IA patients. We employed a larger cohort of patients and validated ORM1 as a potential biomarker for screening of unruptured aneurysm using ELISA. Samples from ruptured aneurysm with vasospasm showed significant upregulation of MMP9 as compared to ruptured aneurysm without vasospasm. Using a cohort of ruptured aneurysm patients with and without vasospasm, we validated MMP9 as a potential biomarker for vasospasm. This study reveals pathophysiology underlying different clinical sub groups of IA and also suggests potential biomarkers.

neuroscience↗

bioRxiv2019

Loss of function from widely distributed, synonymous mutations at single codons

Mutational tolerance inferred from laboratory-based mutational studies is typically much higher than observed natural sequence variation. Using saturation mutagenesis, we show that the ccdA antitoxin component of the ccdAB toxin-antitoxin system is unusually sensitive to mutation with over 60% of mutations leading to loss of function. Multi-base synonymous mutations at a codon display enhanced propensity to show altered phenotypes, relative to single-base ones. Such mutations modulate RNA structure, leading to altered relative translation efficiencies of the two genes in the operon, and a CcdA:CcdB protein ratio below one. These insights were used to predict and experimentally validate synonymous mutations that lead to loss of function in the unrelated relBE operon as well as the lacZ gene. Thus, synonymous mutations can have significant phenotypic effects, in the absence of overexpression or extraneous reporters. More generally, proteins are likely more sensitive to mutation than inferred from previous saturation mutagenesis studies.

molecular biology↗

bioRxiv2019

EpCAM Aptamer siRNA chimeras: Therapeutic efficacy in epithelial cancer cells.

In the era of personalized medicine as well as precision medicine, targeted therapy has become an integral part of cancer treatment in conjunction with conventional chemo- and radiotherapy. We designed aptamer-siRNA chimeras that can specifically target cancers expressing EpCAM, a stem cell marker and deliver the specific siRNA required for therapy response. The siRNAs were chosen against PLK1, BCL2 and STAT3 as these oncogenes play prominent role in tumour progression of several cancers. Targeted delivery of EpCAM-siRNA chimeras resulted in cell death in several cancer cell lines such as cancers of the breast, lung, head and neck, liver and retinoblastoma. In vivo analysis of EpCAM-siRNA chimera mediated silencing on RB xenografts tumour model showed increased tumor reduction in all the three EpCAM-siRNA treated conditions. However, regulation of PLK1 exhibited higher efficacy in tumour reduction. Therefore. We studied signaling mechanism using global phosphoproteomics analysis. An increased P53 mediated downstream signalling pathway might have enabled increased apoptosis in the cancer cells. In conclusion, this study demonstrated the efficacy of EpCAM aptamer chimeras coupled to siRNA gene silencing for targeted anti-cancer therapy.\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC=\"FIGDIR/small/656199v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (48K):\norg.highwire.dtl.DTLVardef@1ce89daorg.highwire.dtl.DTLVardef@bc5daeorg.highwire.dtl.DTLVardef@aa4ceforg.highwire.dtl.DTLVardef@a1159e_HPS_FORMAT_FIGEXP M_FIG C_FIG Illustration showing how EpCAM aptamer-mediated silencing of PLK1 could control the cell cycle progression at multiple number of check points and induce apoptosis involving hyper and hypophosphorylation of variety of signalling molecules

cancer biology↗

bioRxiv2019

Identification of lncRNAs associated with early stage breast cancer and their prognostic implications

Breast cancer is a common malignancy among women with the highest incidence rate worldwide. Dysregulation of long non-coding RNAs occurring in the preliminary stages of breast carcinogenesis is poorly understood. In this study, RNA sequencing was done to identify long non-coding RNA expression profiles associated with early-stage breast cancer. RNA sequencing was done in 6 invasive ductal carcinoma (IDC) tissues along with paired normal tissue samples, 7 ductal carcinoma in situ (DCIS) tissues and 5 apparently normal breast tissues. We identified 375 differentially expressed lncRNAs (DElncRNAs) in IDC tissues compared to paired normal tissues. Antisense transcripts ([~]58%) were the largest subtype among DElncRNAs. About 20% of the 375 DElncRNAs were supported by typical split readings leveraging their detection confidence. Validation was done in n=52 IDC and paired normal tissue by qRT-PCR for the identified targets (ADAMTS9-AS2, EPB41L4A-AS1, WDFY3-AS2, RP11-295M3.4, RP11-161M6.2, RP11-490M8.1, CTB-92J24.3 and FAM83H-AS)1. We evaluated the prognostic significance of DElncRNAs based on TCGA datasets and overexpression of FAM83H-AS1 was associated with patient poor survival. We confirmed that the down-regulation of ADAMTS9-AS2 in breast cancer was due to promoter hypermethylation through in-vitro silencing experiments and pyrosequencing.

cancer biology↗