Biology subjects

Bala, P.

Publications and source records attributed to Bala, P..

5 recordsLinked to original sources

bioRxiv2025

SWI/SNF ATPase Brahma and Notch signaling collaborate with CBP/p300 to regulate neural stem cell apoptosis in Drosophila larval central nervous system.

SWI-SNF ATPase Brahma and Notch signalling are known to interact during development, but how this interaction is executed at the molecular level is not fully understood. We have investigated the molecular mechanism of Brm-Notch interaction in the context of Hox-dependent neural stem cell (NSC) apoptosis in the developing Central Nervous System (CNS) of Drosophila. Our results suggest a multi-tier regulation of NSC apoptosis by Brahma, first by regulating the expression of Drosophila CBP/p300 (Nejire) and the molecular triggers of cell death (Hox, bHLH factor Grainyhead, and Notch signalling pathway). The second mode of regulation is by direct binding of Brahma to the apoptotic enhancer and its collaboration with Notch signalling pathway to regulate the RHG family of apoptotic genes, grim and reaper. Our data support a model where, upon activation of Notch signaling, Brahma and CSL-Su(H)/Mastermind complex recruit CBP/p300 onto the apoptotic enhancer. This increases the H3K27ac marks on the nucleosomes to open up the chromatin and facilitate apoptotic gene transcription in Abd-B and Grh dependent manner.

developmental biology↗

bioRxiv2024

Chemical perturbations impacting histone acetylation governcolorectal cancer differentiation

Dysregulated epigenetic programs that restrict differentiation, reactivate fetal genes, and confer phenotypic plasticity are critical to colorectal cancer (CRC) development. By screening a small molecule library targeting epigenetic regulators using our dual reporter system, we found that inhibiting histone deacetylase (HDAC) 1/2 promotes CRC differentiation and anti-tumor activity. Comprehensive biochemical, chemical, and genetic experiments revealed that on-target blockade of the HDAC1/2 catalytic domain mediated the differentiated phenotype. Unbiased profiling of histone posttranslational modifications induced by HDAC1/2 inhibition nominated acetylation of specific histone lysine residues as potential regulators of differentiation. Genome-wide assessment of implicated marks indicated that H3K27ac gains at HDAC1/2-bound regions associated with open chromatin and upregulation of differentiation genes upon HDAC1/2 inhibition. Disrupting H3K27ac by degrading acetyltransferase EP300 rescued HDAC1/2 inhibitor-mediated differentiation of a patient-derived CRC model using single cell RNA-sequencing. Genetic screens revealed that DAPK3 contributes to CRC differentiation induced by HDAC1/2 inhibition. These results highlight the importance of specific chemically targetable histone modifications in governing cancer cell states and epigenetic reprogramming as a therapeutic strategy in CRC. BRIEF SUMMARYHDAC1/2 inhibition promotes colorectal cancer differentiation via gains in H3K27ac, which can be reversed by blocking its acetyltransferase EP300.

cancer biology↗

bioRxiv2022

Developmental reprogramming mediates aberrant cell state plasticity in colorectal cancer initiation

Cell state (phenotypic) plasticity is a carefully regulated feature of adult epithelial cells that enables adaptive responses to injury, inflammation, and other forms of stress. Aberrant expansion of the normally restricted capability for cell state plasticity to escape terminal differentiation is a critical aspect of neoplasia. The nongenetic factors and specific programs that mediate aberrant cell state plasticity and impaired differentiation require deeper characterization to understand this elusive aspect of cancer pathogenesis. Using genetically engineered and carcinogen-induced murine models of intestinal neoplasia, we demonstrate that impaired differentiation is a conserved event preceding cancer development. Single cell RNA-sequencing (scRNA-seq) of neoplastic intestinal lesions from both mouse models and a patient with familial adenomatous polyposis revealed that cancer initiates by adopting an aberrant transcriptional state characterized by nonoverlapping expression of a regenerative pathway, marked by Ly6a (Sca-1), and a fetal intestinal program, positive for Tacstd2 (Trop2). Genetic inactivation of Sox9 prevented adenoma formation in ApcKO mice, obstructed emergence of aberrant regenerative and fetal intestinal programs, and restored multi-lineage differentiation by scRNA-seq. Expanded chromatin accessibility at regeneration and fetal genes upon Apc inactivation was reduced by concomitant Sox9 suppression. These studies indicate that aberrant cell state plasticity mediated by unabated regenerative activity and developmental reprogramming precedes cancer development.

cancer biology↗

bioRxiv2022

To βor not to β: Lack of correlation between APC mutation and β-catenin nuclear localization in colorectal cancer

Colorectal cancer (CRC) appears to arise from sequential genetic lesions in tumor suppressor genes (APC, SMAD4 and TP53) and oncogenes (KRAS) leading to the classical adenoma to carcinoma progression. Biallelic APC inactivating genetic aberrations are detected in about 70% of early microadenomas implicating APC inactivation as the first genetic hit in CRC. APC is an essential protein of the Wnt destruction complex; APC inactivation is believed to cause disruption of the complex allowing stabilization and nuclear translocation of {beta}-catenin, resulting in transcriptional activation of cancer-promoting genes. Here, we provide evidence for a surprising lack of correlation between APC mutation and {beta}-catenin nuclear localization in early-onset sporadic rectal cancer samples. {beta}-catenin nuclear localization and APC mutation were validated from serial FFPE sections representing same tumor regions. Several factors including status of KRAS mutation could not explain the absence of {beta}-catenin nuclear localization in tumor samples harboring APC mutation. This lack of correlation was validated in CRC cell lines harboring various APC mutations. Our results provide evidence directly from tumor samples for possible non-canonical role(s) for mutant APC.

cancer biology↗

bioRxiv2020

Exome sequencing identifies ARID2 as a novel tumor suppressor in early-onset sporadic rectal cancer

Early-onset sporadic rectal cancer (EOSRC) is a unique and predominant colorectal cancer (CRC) subtype in India. In order to understand the tumorigenic process in EOSRC, we performed whole exome sequencing of 47 microsatellite stable EOSRC samples. Signature 1 was the predominant mutational signature in EOSRC, as previously shown in other CRC exome studies. More importantly, we identified TP53, KRAS, APC, PIK3R1 and SMAD4 as significantly mutated (q<0.1) and ARID1A and ARID2 as near-significantly mutated (restricted hypothesis testing; q<0.1) candidate drivers. Unlike the other candidates, the tumorigenic potential of ARID2, encoding a component of the SWI/SNF chromatin remodeling complex, is largely unexplored in CRC. shRNA mediated ARID2 knockdown performed in two different CRC cell lines resulted in significant alterations in transcript levels of cancer-related target genes. More importantly, ARID2 knockdown promoted several tumorigenic features including cell viability, proliferation, ability to override contact inhibition of growth, and migration besides significantly increasing tumor formation ability in nude mice. The observed gain in tumorigenic features were rescued upon ectopic expression of ARID2. Analyses of the TCGA CRC dataset revealed poorer survival in patients with ARID2 alterations. We therefore propose ARID2 as a novel tumor suppressor in CRC.

cancer biology↗