Biology subjects

Bialik, S.

Publications and source records attributed to Bialik, S..

5 recordsLinked to original sources

bioRxiv2024

The RNA-binding protein PRRC2B preserves 5' TOP mRNA during starvation to maintain ribosome biogenesis during nutrient recovery

PRRC2B is an intrinsically disordered RNA-binding protein that is part of the cells translation machinery. Here we show that PRRC2B has two alternatively spliced mRNA transcripts producing major long and minor short isoforms. Mass spectrometry-based interaction studies indicated that both isoforms associate with the 40S ribosomal subunit and translation initiation factors. Importantly, the long isoform also interacted with additional RNA-binding proteins through its unique Arg/Gly-rich region. Among these is LARP1, a regulator of 5 terminal oligopyrimidine (TOP) mRNAs under conditions of mTOR inhibition. We discovered that like LARP1, PRRC2B is necessary for preservation of 5 TOP mRNA levels, particularly those encoding ribosomal proteins, during amino acid starvation. In its absence, the rapid de novo translation of ribosomal proteins that takes place upon nutrient recovery is impeded. Overall, our study elucidates a newly discovered function for PRRC2B as an RNA-binding protein that regulates ribosomal biogenesis upon metabolic shift, in addition to its established function in initiating translation of specific mRNA targets.

molecular biology↗

bioRxiv2023

Loss of EIF4G2 Mediates Aggressiveness in Distinct Human Endometrial Cancer Subpopulations with Poorer Survival Outcome in Patients

The non-canonical translation initiation factor EIF4G2 plays essential roles in embryonic development and differentiation, and contributes to the cellular stress response via translation of selective mRNA cohorts. Currently there is limited and conflicting information regarding the potential involvement of EIF4G2 in cancer development and progression. Endometrial cancer (EC) is the most pervasive gynecological cancer in the developed world, with increasing incidence every year. High grade ECs are largely refractory to conventional treatments, presenting poor survival rates and lacking suitable prognostic markers. Here we assayed a cohort of 280 EC patients across different types, grades, and stages, and found that low EIF4G2 expression highly correlated with poor overall and recurrence free survival in Grade 2 EC patients, monitored over a period of up to 12 years. To establish a causative connection between low EIF4G2 expression and cancer progression, we analyzed in parallel two independent human EC cell lines and demonstrated that stable EIF4G2 knock-down resulted in increased resistance to conventional therapies. Depletion of EIF4G2 also increased the prevalence of molecular markers for aggressive cell subsets, and altered their transcriptional and proteomic landscapes. Prominent among the proteins with decreased abundance were Kinesin-1 motor proteins KIF5B and KLC1, 2, 3. Multiplexed imaging of the tumors from this EC patient cohort showed a correlation between decreased protein expression of either KIF5B or KLC1, and poor survival in patients of certain grades and stages. The findings herein reveal potential novel biomarkers for Grade 2 EC with potential ramifications for patient stratification and therapeutic interventions. SignificanceDecreased EIF4G2 protein results in increased drug resistance of aggressive sub-populations of endometrial cancer cells, is associated with poor patient survival, and may serve as a novel prognosis marker for endometrial cancer.

cancer biology↗

bioRxiv2023

Loss-of-function cancer-associated mutations in the EIF4G2 non-canonical translation initiation factor

Tumor cells often exploit the protein translation machinery, resulting in enhanced protein expression essential for tumor growth. Since canonical translation initiation is often suppressed due to cell stress in the tumor microenvironment, non-canonical translation initiation mechanisms become particularly important for shaping the tumor proteome. EIF4G2 is a non-canonical translation initiation factor that mediates internal ribosome entry site [IRES] and upstream open reading frame [uORF] dependent initiation mechanisms, which can be used to modulate protein expression in cancer. Here we explored the contribution of EIF4G2 to cancer by screening the COSMIC database for EIF4G2 somatic mutations in cancer patients. Functional examination of missense mutations revealed deleterious effects on EIF4G2 protein-protein interactions, and importantly, on its ability to mediate non-canonical translation initiation. Specifically, one mutation, R178Q, led to reductions in protein expression and near complete loss-of-function. Two other mutations within the MIF4G domain specifically affected EIF4G2s ability to mediate IRES-dependent translation initiation but not that of target mRNAs with uORFs. These results shed light on both the structure-function of EIF4G2 and its potential tumor suppressor effects.

cancer biology↗

bioRxiv2021

The Serine Protease HtrA2 mediates radiation-induced senescence in cancer cells

Radiation therapy can induce cellular senescence in cancer cells leading to short-term tumor growth arrest, yet increased long-term recurrence. To better understand the molecular mechanisms involved, we developed a model of radiation-induced senescence in cultured cancer cells, which exhibited a typical senescent phenotype, including upregulation of p53 and its target p21, followed by sustained reduction in cellular proliferation, changes in cell size and cytoskeleton organization, and senescence-associated beta-galactosidase activity. A functional siRNA screen using a cell death-related library identified the mitochondrial Ser protease HtrA2 as necessary for senescence development. Mass spectrometry-based proteomic profiling of the senescent cells indicated downregulation of proteins involved in cell cycle progression and DNA repair, and upregulation of proteins associated with malignancy, while irradiation with HtrA2 inhibition upregulated cell proliferation components. In search of direct HtrA2 substrates following radiation, we determined that HtrA2 cleaves the intermediate filament protein vimentin, affecting its cytoplasmic organization. Ectopic expression of active cytosolic HtrA2 resulted in similar changes to vimentin filament assembly. Thus HtrA2, contributes to several hallmarks of senescence and is involved in the cytoskeletal reorganization that accompanies radiation-induced senescence. SummaryHere the authors identify the Ser protease HtrA2 as a novel mediator of radiation-induced senescence, necessary for sustained proliferation arrest and reorganization of the vimentin filament network.

cancer biology↗

bioRxiv2020

A functional pre-screening platform for identifying points of vulnerability in the cell death map of human melanoma tumors

Targeted drug therapy in melanoma patients carrying the BRAF V600E mutation provides temporary remission, often followed by relapse due to acquired drug resistance. Here we propose a functional approach to circumvent drug resistance by applying a personalized prescreening platform that maps points of vulnerability in each tumor, prior to drug treatment. This platform applies siRNAs targeting 81 apoptosis, autophagy and programmed necrosis genes in patient tumor cell cultures, identifying genes whose targeting maximizes cell killing by short-term BRAF inhibition. Melanoma tumors displayed large heterogeneity in the number and identities of soft-spots, providing different tumor-specific functional death signatures. The soft-spots were targeted by replacing functional siRNAs with small compound inhibitors for long-term treatment in combination with vemurafenib. This strategy reduced the number of drug-tolerant persister cells surviving treatment, and most importantly, the number of drug-resistant foci. Thus, prescreening melanoma tumors for soft-spots within the cell death network may enhance targeted drug therapy before resistance emerges, thereby reducing the odds of developing drug-resistant mutations, and preventing tumor relapse.

cancer biology↗