Biology subjects

Budhiraja, S.

Publications and source records attributed to Budhiraja, S..

5 recordsLinked to original sources

bioRxiv2025

Genomic insights into six clinical isolates of Stenotrophomonas maltophilia from Northern India

Stenotrophomonas maltophilia is a gram-negative opportunistic pathogen that causes respiratory, urinary and bloodstream infections. Due to rising prevalence of difficult to treat S. maltophilia infections, it is considered as one of the important pathogens in many regions, including India. Despite its importance in public health, very few studies provide detailed characterization of the genomes of clinical isolates of S. maltophilia. In this study, we sequence six isolates of S. maltophilia from a tertiary healthcare centre in the Northern India. Along with the culture sensitivity, we report the genomic underpinnings of resistance and virulence in these isolates. In three out of six isolates, we identify a rare beta-lactamase gene kbl-1 that can confer resistance to variety of beta-lactam antibiotics. Though truncated in two isolates, an intact copy of kbl-1 is present in the third isolate. This intact copy of kbl-1 is flanked by insertion elements that are commonly found in several pathogenic species indicating high potential for horizontal gene transfer. To the best of our knowledge, this is a first report of kbl-1 in S. maltophilia from India. ImportanceAntimicrobial resistance (AMR) is one of the biggest global public health challenges. Tackling AMR gets complicated as diverse pathogenic species are involved and resistance is manifested against several different kinds of antibiotics. Genomic surveillance of the resistant pathogens is a key to fight this global threat and needs to extend to important emerging pathogens as well. Here we report genomic sequences and associated characteristics of six Stenotrophomonas maltophilia isolates from Northern India. Along with several resistance and virulence genes we also discover a rare beta-lactamase, blaKBL-1, gene with a high potential of transfer to other species. blaKBL-1 beta-lactamase confers resistance to several beta-lactam antibiotics like ampicillin, amoxicillin, penicillin G, piperacillin, ceftazidime and cefozopran. This is the first report of the presences of this beta-lactamase from India.

microbiology↗

bioRxiv2024

THOC1 complexes with SIN3A to regulate R-loops and promote glioblastoma progression

ABSTRACTGlioblastoma (GBM), the most common and aggressive malignant brain tumor in adults, has a median survival of 21 months. To identify drivers of GBM proliferation, we conducted a CRISPR-knockout screen, which revealed THO Complex 1 (THOC1) as a key driver. Knocking down THOC1 significantly reduced GBM cell viability across patient-derived xenograft (PDX) lines, enhancing survival (p<0.01) in primary PDX models. Conversely, overexpressing THOC1 in non-cancerous cells bolstered viability, decreasing survival and causing tumor engraftment in vivo (p<0.01). Further investigation revealed THOC1s robust interaction with SIN3A, a histone deacetylase complex. Histone deacetylation has been previously shown to prevent the buildup of R-loops, structures that form normally during transcription but can be lethal in excess. We found that THOC1-knockdown leads to elevated R-loop levels and reduced histone deacetylation levels. Next, to understand the networks specifically regulated by THOC1-mediated R-loop prevention, we conducted unbiased RNA-sequencing on control and THOC1-knockdown GBM cells. We found that THOC1s role in R-loop prevention primarily affects telomeres, critical regions for cell replication. We further show that THOC1-knockdown results in significantly increased telomeric R-loop levels and shortened telomeres. Ultimately, this study suggests that targeting THOC1 shows promise as a therapeutic strategy to disrupt the delicate R-loop landscape and undermine GBMs replicative potential.

cancer biology↗

bioRxiv2021

Ribonucleotide Reductase Regulatory Subunit M2 as a Driver of Glioblastoma TMZ-Resistance through Modulation of dNTP Production

Glioblastoma (GBM) remains one of the most resistant and fatal forms of cancer. Previous studies have examined primary and recurrent GBM tumors, but it is difficult to study tumor evolution during therapy where resistance develops. To investigate this, we performed an in vivo single-cell RNA sequencing screen in a patient-derived xenograft (PDX) model. Primary GBM was modeled by mice treated with DMSO control, recurrent GBM was modeled by mice treated with temozolomide (TMZ), and during therapy GBM was modeled by mice euthanized after two of five TMZ treatments. Our analysis revealed the cellular population present during therapy to be distinct from primary and recurrent GBM. We found the Ribonucleotide Reductase gene family to exhibit a unique signature in our data due to an observed subunit switch to favor RRM2 during therapy. GBM cells were shown to rely on RRM2 during therapy causing RRM2-knockdown (KD) cells to be TMZ-sensitive. Using targeted metabolomics, we found RRM2-KDs to produce less dGTP and dCTP than control cells in response to TMZ (p<0.0001). Supplementing RRM2-KDs with deoxycytidine and deoxyguanosine rescued TMZ-sensitivity, suggesting an RRM2-driven mechanism of chemoresistance, established by regulating the production of these nucleotides. In vivo, tumor-bearing mice treated with the RRM2-inhibitor, Triapine, in combination with TMZ, survived longer than mice treated with TMZ alone (p<0.01), indicating promising clinical opportunities in targeting RRM2. Our data present a novel understanding of RRM2 activity, and its alteration during therapeutic stress as response to TMZ-induced DNA damage.

cancer biology↗

bioRxiv2021

CRISPR-Cas9 Screen Reveals PSMB3 Contributes to Gliomagenesis Through Proteasome-Dependent and Independent Mechanisms

Glioblastoma (GBM) is the most common adult malignant brain tumor, with a median survival of 21 months and a 100% recurrence rate. Even though many of the critical oncogenic drivers for GBM have been identified, the basis of gliomagenesis is still under investigation. To identify novel genes that contribute to GBM progression, we performed a genome-wide CRISPR-Cas9 knockout screen. We identified four previously unstudied genes - PSMB3, CHCHD4, SPDYE5, HSPA1 - which had elevated expression in cancer and demonstrated a significant positive correlation with respect to GBM growth and patient survival in vivo and patient datasets. Furthermore, overexpression of PSMB3 and HSPA5 in neural stem cells resulted in transformation to a cancer phenotype. Further investigation of PSMB3, a subunit of the proteasome, allowed us to identify both ubiquitin-mediated and non-ubiquitin-mediated mechanisms of oncogenesis. Ultimately, the data from our CRISPR screens suggests that these genes drive tumor progression, making them promising therapeutic targets for GBM.

cancer biology↗

bioRxiv2021

ARF4-mediated Retrograde Trafficking Drives Chemoresistance in Glioblastoma

Glioblastoma (GBM) is the most common type of adult malignant brain tumor, with a median survival of only 21 months. This is partly due to the high rate of resistance to conventional therapy, including temozolomide (TMZ), leading to recurrence rates close to 100%. It still remains unknown what drives the development of this resistance. To identify the unknown genes driving the development of this resistance, we performed a genome-wide CRISPR knockout screen comparing a DMSO-treated population with a TMZ-treated population over 14 days. We identified 4 previously unstudied genes - ARF4, PLAA, SPTLC1, and PIGK - that showed significant elevations in expression in recurrent tumors in patient datasets, along with significant survival benefits corresponding to low gene expression. Further investigation of ARF4, known to be involved in retrograde trafficking, allowed us to identify a mechanism of resistance that is mediated by increased retrograde transport of EGFR into the nucleus. Ultimately, our CRISPR-Cas9 screen has identified a promising therapeutic target, ARF4, which may drive GBMs high resistance to chemotherapy.

cancer biology↗