Biology subjects

Maity, T. K.

Publications and source records attributed to Maity, T. K..

10 recordsLinked to original sources

bioRxiv2026

Direct Mapping of CDK2 Substrates in Embryonic Stem Cells Uncovers an AP-Site Repair Mechanism via HMCES Phosphorylation

Embryonic stem cells (ESCs) proliferate rapidly while robustly maintaining genomic integrity and exhibiting high cell-cycle kinase activity. How this activity contributes to genome integrity remains unclear. Here, using mouse ESCs engineered to express an analog-sensitive CDK2, we combine thiophosphate labeling with mass spectrometry to define a high-confidence CDK2 substrate landscape. We uncovered 65 CDK2 substrates in total, including both known and previously unrecognized substrates. Among these, HMCES, a sensor of apurinic/apyrimidinic (AP) sites, was identified as a specific cyclin E-CDK2 substrate. We mapped three CDK2-dependent phosphorylation sites in HMCES and showed that phosphorylation of these sites decreased HMCES binding to ssDNA. Mutational analysis further revealed that HMCES docks to cyclin E-CDK2 complexes via the hydrophobic patch on cyclin E. Finally, we demonstrated that HMCES phosphorylation contributes to AP-site repair and promotes ESC proliferation. Together, our findings uncover a CDK2-HMCES signaling axis that links rapid cell-cycle progression to the preservation of genome stability in mouse ESCs.

developmental biology↗

bioRxiv2026

Global Proteomics Investigation of SAMT-247 Targets: An Antiviral Thioester that Acetylates Zinc Finger Proteins

Covalent modification of target proteins is a well-established mechanism of action for small molecule inhibitors. Cysteine residues in particular have been exploited for their reactivity toward electrophilic molecules. SAMT-247 is a mercaptobenzamide thioester that covalently acetylates cysteines in the zinc-coordinating domains of the HIV nucleocapsid protein. This SAMT-247-promoted reaction leads to loss of zinc binding by the protein, with concomitant loss of protein structure and function. Although it has low cytotoxicity in animal models, recent studies have indicated that it affects other protein targets in uninfected cells, for example leading to increased immune cell functions. In this study, global proteomics approaches have been used to better understand other protein targets of SAMT-247. Minimal effects are observed when unstimulated THP-1 monocyte cells were treated with SAMT-247. In contrast, thermal proteome profiling identified 170 proteins with altered thermal stability when THP-1 cells were stimulated with phorbol 12-myristate 13-acetate/Ionomycin (PMA/Iono) before SAMT-247 treatment. Among the affected proteins, 81 contain a zinc-coordinating domain and/or have been shown to have a reactive cysteine residue. Among these, several play a role in cellular metabolism, and Seahorse assays demonstrated that SAMT-247 significantly increased the anti-metabolic and pro-glycolytic effect of PMA/Iono in THP-1 cells. Two of the most-affected proteins were ZC3H7A, a microRNA-binding protein with four zinc finger domains, and MGMT, a DNA damage repair protein with a reactive cysteine. Both proteins were modified by SAMT-247 when tested alone or in the presence of THP-1 cell lysate, indicating that they are bona fide targets of the inhibitor. The low activity of SAMT-247 in unstimulated THP-1 cells is consistent with its low cytotoxicity. The increased effects of SAMT-247 in stimulated immune cells suggests that this molecule could be developed to target diseases other than HIV.

cell biology↗

bioRxiv2026

16S ribosomal RNA modification drives transcript-specific translation efficiency

Bacterial ribosomal RNAs (rRNAs) are decorated with conserved nucleotide modifications, but the functionality of these modifications is often underexplored. MraW (RsmH) is a 16S rRNA methyltransferase that fine-tunes ribosomal function. We identified a loss-of-function allele in mraW that corrected a late-stage sporulation defect in Bacillus subtilis by bypassing a key sporulation checkpoint via altered translational regulation. Purified ribosomes isolated from {Delta}mraW cells displayed a [~]2-fold decrease in translation efficiency; in vivo, {Delta}mraW cells produced decreased levels of the sporulation checkpoint protein CmpA. This regulation was mediated by sequences from the 5 untranslated region and the coding sequence of cmpA, which form a step-loop structure that occlude early codons of the mRNA. Proteomic analysis revealed that MraW directly or indirectly regulates the production of multiple proteins, some of which form similar structural elements as the cmpA transcript. We propose that MraW modification of 16S rRNA enhances translation efficiency in general, and that specific transcripts, whose gene products are likely required in limiting quantities, have evolved structural features that act as a regulatory mechanism to govern protein levels. This type of regulation may be most apparent in bacteria which exhibit uncoupled transcription and translation. HIGHLIGHTSO_LIA conserved 16S rRNA modification enhances translation of structured mRNAs C_LIO_LIEarly mRNA stem-loops impose translational control dependent on ribosome modification C_LIO_LImRNA structure and rRNA modifications likely co-evolved to fine-tune protein dosage C_LI

microbiology↗

bioRxiv2026

Enteroviral epitope mimicry enables NK cell-mediated targeting of ASPH in hepatocellular carcinoma

Cancer development is shaped by host-microbe interactions, including viral infections. While several viruses are established oncogenic drivers, their potential protective roles in cancer remain unclear. Here we identify a dominant antibody response to CE1, a consensus epitope of enterovirus and rhinovirus, that is associated with reduced hepatocellular carcinoma (HCC) incidence and mortality. Anti-CE1 antibodies selectively recognize HCC cells and mediate anti-tumor activity through NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC). Mechanistically, anti-CE1 antibodies cross-react with aspartate {beta}-hydroxylase (ASPH), with CE1-ASPH sequence homology underpinning tumor recognition and cytotoxicity. Clinically, ASPH is aberrantly upregulated in HCC and correlates with inferred NK cell-associated ADCC activity and improved survival in CE1-seropositive patients. Collectively, these findings reveal a mechanism by which antiviral humoral immunity confers cancer protection through molecular mimicry and highlight anti-CE1 immunity as a potential therapeutic strategy in HCC.

cancer biology↗

bioRxiv2023

YAP localization mediates mechanical adaptation of human cancer cells during extravasation in vivo

Biophysical profiling of primary tumors has revealed that individual tumor cells fall along a highly heterogeneous continuum of mechanical phenotypes. One idea is that a subset of tumor cells is "softer" to facilitate detachment and escape from the primary site, a step required to initiate metastasis. However, it has also been postulated that cells must be able to deform and generate sufficient force to exit into distant sites. Here, we aimed to dissect the mechanical changes that occur during extravasation and organ colonization. Using multiplexed methods of intravital microscopy and optical tweezer based active microrheology, we obtained longitudinal images and mechanical profiles of cells during organ colonization in vivo. We determined that cells were softer, more liquid like upon exit of the vasculature but stiffened and became more solid like once in the new organ microenvironment. We also determined that a YAP mediated mechanogenotype influenced the global dissemination in our in vivo and in vitro models and that reducing mechanical heterogeneity could reduce extravasation. Moreover, our high throughput analysis of mechanical phenotypes of patient samples revealed that this mechanics was in part regulated by the external hydrodynamic forces that the cancer cells experienced within capillary mimetics. Our findings indicate that disseminated cancer cells can keep mutating with a continuum landscape of mechano-phenotypes, governed by the YAP-mediated mechanosensing of hydrodynamic flow.

biophysics↗

bioRxiv2023

Flap endonuclease 1 repairs DNA-protein crosslinks via ADP-ribosylation

DNA-protein crosslinks (DPCs) are among the most ubiquitous and detrimental DNA lesions which arise from exposure to metabolic stresses, drugs, or crosslinking agents such as formaldehyde (FA). FA is a cellular by-product of methanol metabolism, histone demethylation, lipid peroxidation as well as environmental pollutants. Failure to repair FA-induced DPCs blocks nearly all chromatin-based processes including replication and transcription, leading to immunodeficiencies, neurodegeneration, and cancer. Yet, it remains largely unknown how the cell repairs DPCs. The study of DPC repair is impeded by our incomprehension of the types of proteins crosslinked by FA due to the lack of techniques to identify the DPCs. Here, we designed a novel bioassay to profile FA-induced DPCs by coupling cesium chloride differential ultracentrifugation with HPLC-mass spectrometry (MS). Using the method, we revealed the proteome of FA-induced DPCs in human cells and found that the most abundant proteins that form DPCs are PARP1, topoisomerases I and II, methyltransferases, DNA and RNA polymerases, histones, as well as ribosomal proteins. To identify enzymes that repair DPCs, we carried out RNA interference screening and found that downregulation of flap endonuclease 1 (FEN1) rendered cells hypersensitive to FA. Since FEN1 possesses 5-flap endonuclease activity, we hypothesized that FA induces DPC-conjugated 5-flap DNA fragments that can be processed by FEN1. Indeed, we demonstrate that FA damages DNA bases that are converted into 5-flap via the base excision pathway (BER). We also observed that the damaged DNA bases were colocalized with DPCs and FEN1. Mechanistically, we showed that FEN1 repairs FA-induced DPCs in vivo and cleaves 5-flap DNA substrate harboring DPC mimetic in vitro. We also found that FEN1 repairs enzymatic topoisomerase II (TOP2)-DPCs induced by their inhibitors etoposide and doxorubicin independently of the BER pathway, and that FEN1 and the DPC-targeting protease SPRTN act as parallel pathways for the repair of both FA-induced non-enzymatic DPCs and etoposide-induced enzymatic TOP2-DPCs. Notably, we found that FA-induced non-enzymatic DPCs and enzymatic TOP2-DPCs are promptly modified by poly-ADP-ribosylation (PARylation), a post-translational modification catalyzed by PARP1, a key DNA damage response effector that acts by PARylating both DNA damage sites and DNA repair proteins. We performed immunoprecipitation (IP) assays with anti-PAR antibody for HPLC-MS and identified FEN1 as a PARylation substrate. Next, we showed that PARylation of DPC substrates signaled FEN1 whereas PARylation of FEN1 drove FEN1 to DPC sites. Finally, using the enzymatic labeling of the terminal ADP-ribose-MS method, we identified the E285 residue of FEN1 as a dominant PARylation site, which appeared to be required for FEN1 relocation to DPCs. Taken together, our work not only unveiled the identities of FA-induced DPCs but also discovered an unprecedented PARP1-FEN1 nuclease pathway as a universal and imperative mechanism to repair the miscellaneous DPCs and prevent DPC-induced genomic instability.

molecular biology↗

bioRxiv2022

The homeobox transcription factor DUXBL controls exit from totipotency

Upon exit from the totipotent 2-cell (2C) embryo stage, the 2C-associated transcriptional program needs to be efficiently silenced. However, the molecular mechanisms involved in this process remain mostly unknown. Here, we demonstrate that the 2C-specific transcription factor DUX directly induces the expression of DUXBL to promote this silencing. Indeed, DUX expression in Duxbl-knockout ESC causes increased induction of the 2C-transcriptional program, whereas DUXBL overexpression impairs 2C-associated transcription. CUT&RUN analyses show that DUXBL gains accessibility to DUX-bound regions in DUX-induced ESC while it is unable to bind those regions in uninduced cells. Mechanistically, we determined that DUXBL interacts with TRIM24 and TRIM33, two members of the tripartite motif superfamily involved in gene silencing and co-localizes with them in nuclear foci upon DUX expression. Furthermore, DUXBL downregulation in mouse zygotes leads to a penetrant 2C-stage arrest. Our data reveals an unexpected role for DUXBL in controlling the exit from totipotency.

developmental biology↗

bioRxiv2020

Proteogenomic analysis unveils the HLA Class I presented immunopeptidome in melanoma and EGFR mutant lung adenocarcinoma

Immune checkpoint inhibitor and adoptive lymphocyte transfer-based therapies have shown great therapeutic potential for cancers with high tumor mutation burden (TMB). Here, we employed mass spectrometry (MS)-based proteogenomic large-scale profiling to identify potential immunogenic human leukocyte antigen (HLA) Class I-presented peptides in both melanoma, a "hot tumor" with high TMB, and EGFR mutant lung adenocarcinoma, a "cold tumor" with low TMB. We identified several classes of neopeptides, including mutated neoantigens and more than 1000 post-translationally modified peptides representing 58 different PTMs. We constructed a cancer germline (CG) antigen database with 285 antigens and identified 42 Class I-presented CG antigens. Finally, we developed a non-canonical peptide discovery pipeline to identify 44 lncRNA-derived peptides and validated Class I binding for select neopeptides. We provide direct evidence of HLA Class I presentation of a large number of neopeptides for potential vaccine or adoptive cell therapy in melanoma and mutant EGFR lung cancer.

immunology↗

bioRxiv2018

Quantitative mass spectrometry to interrogate proteomic heterogeneity in metastatic lung adenocarcinoma and validate a novel somatic mutation CDK12-G879V

Lung cancer is the leading cause of cancer death both in men and women. Tumor heterogeneity is an impediment to targeted treatment of all cancers, including lung cancer. Here, we sought to characterize changes in tumor proteome and phosphoproteome by longitudinal, prospective collection of tumor tissue of an exceptional responder lung adenocarcinoma patient who survived with metastatic lung adenocarcinoma for more than seven years with HER2-directed therapy in combination with chemotherapy. We employed \"Super-SILAC\" and TMT labeling strategies to quantify the proteome and phosphoproteome of a lung metastatic site and ten different metastatic progressive lymph nodes collected across a span of seven years, including five lymph nodes procured at autopsy. We identified specific signaling networks enriched in lung compared to the lymph node metastatic sites. We correlated the changes in protein abundance with changes in copy number alteration (CNA) and transcript expression. To further interrogate the mass spectrometry data, patient-specific database was built incorporating all the somatic variants identified by whole genome sequencing (WGS) of genomic DNA from the lung, one lymph node metastatic site and blood. An extensive validation pipeline was built for confirmation of variant peptides. We validated 360 spectra corresponding to 55 germline and 6 somatic variant peptides. Targeted MRM assays demonstrated expression of two novel variant somatic peptides, CDK12-G879V and FASN-R1439Q, with expression in lung and lymph node metastatic sites, respectively. CDK12 G879V mutation likely results in a nonfunctional CDK12 kinase and chemotherapy susceptibility in lung metastatic sites. Knockdown of CDK12 in lung adenocarcinoma cells results in increased chemotherapy sensitivity, explaining the complete resolution of the lung metastatic sites in this patient.

cancer biology↗

bioRxiv2018

Integrated proteogenomic analysis of metastatic thoracic tumors identifies APOBEC mutagenesis and copy number alterations as drivers of proteogenomic tumor evolution and heterogeneity

Elucidation of the proteogenomic evolution of metastatic tumors may offer insight into the poor prognosis of patients harboring metastatic disease. We performed whole-exome and transcriptome sequencing, copy number alterations (CNA) and mass spectrometry-based quantitative proteomics of 37 lung adenocarcinoma (LUAD) and thymic carcinoma (TC) metastases obtained by rapid autopsy and found evidence of patient-specific, multi-dimensional heterogeneity. Extreme mutational heterogeneity was evident in a subset of patients whose tumors showed increased APOBEC-signature mutations and expression of APOBEC3 region transcripts compared to patients with lesser mutational heterogeneity. TP53 mutation status was associated with APOBEC hypermutators in our cohort and in three independent LUAD datasets. In a thymic carcinoma patient, extreme heterogeneity and increased APOBEC3AB expression was associated with a high-risk germline APOBEC3AB variant allele. Patients with CNA occurring late in tumor evolution had corresponding changes in gene expression and protein abundance indicating genomic instability as a mechanism of downstream transcriptomic and proteomic heterogeneity between metastases. Across all tumors, proteomic heterogeneity was greater than copy number and transcriptomic heterogeneity. Enrichment of interferon pathways was evident both in the transcriptome and proteome of the tumors enriched for APOBEC mutagenesis despite a heterogeneous immune microenvironment across metastases suggesting a role for the immune microenvironment in the expression of APOBEC transcripts and generation of mutational heterogeneity. The evolving, heterogeneous nature of LUAD and TC, through APOBEC-mutagenesis and CNA illustrate the challenges facing treatment outcomes.

cancer biology↗