Stephanie Jocelyne Sungalee

Histone acetylation dynamics modulates chromatin conformation and allele-specific interactions at oncogenic loci

Giovanni Ciriello, Natalya Katanayeva, Ruxandra-Andreea Lambuta, Elisa Oricchio, Stephanie Jocelyne Sungalee

In cancer cells, enhancer hijacking mediated by chromosomal alterations and/or increased deposition of acetylated histone H3 lysine 27 (H3K27ac) can support oncogene expression. However, how the chromatin conformation of enhancer-promoter interactions is affected by these events is unclear. In the present study, by comparing chromatin structure and H3K27ac levels in normal and lymphoma B cells, we show that enhancer-promoter-interacting regions assume different conformations according to the local abundance of H3K27ac. Genetic or pharmacological depletion of H3K27ac decreases the frequency and the spreading of these interactions, altering oncogene expression. Moreover, enhancer hijacking mediated by chromosomal translocations influences the epigenetic status of the regions flanking the breakpoint, prompting the formation of distinct intrachromosomal interactions in the two homologous chromosomes. These interactions are accompanied by allele-specific gene expression changes. Overall, our work indicates that H3K27ac dynamics modulates interaction frequency between regulatory regions and can lead to allele-specific chromatin configurations to sustain oncogene expression. Enhancer-promoter three-dimensional interactions at oncogenic loci are modulated by H3K27ac dynamics. Enhancer hijacking mediated by chromosomal translocations leads to distinct chromatin states, intrachromosomal interactions and allele-specific gene expression.

2021

Systematic inference and comparison of multi-scale chromatin sub-compartments connects spatial organization to cell phenotypes

Giovanni Ciriello, Marco Mina, Elisa Oricchio, Stephanie Jocelyne Sungalee

Chromatin compartmentalization reflects biological activity. However, inference of chromatin sub-compartments and compartment domains from chromosome conformation capture (Hi-C) experiments is limited by data resolution. As a result, these have been characterized only in a few cell types and systematic comparisons across multiple tissues and conditions are missing. Here, we present Calder, an algorithmic approach that enables the identification of multi-scale sub-compartments at variable data resolution. Calder allows to infer and compare chromatin sub-compartments and compartment domains in >100 cell lines. Our results reveal sub-compartments enriched for poised chromatin states and undergoing spatial repositioning during lineage differentiation and oncogenic transformation. Computational algorithms to infer chromatin sub-compartments and compartment domains require high-resolution Hi-C maps. Here the authors present Calder, an algorithm that can infer sub-compartments and compartment domains with variable resolution Hi-C data, and they apply it to more than a hundred Hi-C experiments to study sub-compartment repositioning.

NATURE RESEARCH2021

A scalable CRISPR/Cas9-based fluorescent reporter assay to study DNA double-strand break repair choice

Stephanie Jocelyne Sungalee

Double-strand breaks (DSBs) are the most toxic type of DNA lesions. Cells repair these lesions using either end protection- or end resection-coupled mechanisms. To study DSB repair choice, we present the Color Assay Tracing-Repair (CAT-R) to simultaneously quantify DSB repair via end protection and end resection pathways. CAT-R introduces DSBs using CRISPR/Cas9 in a tandem fluorescent reporter, whose repair distinguishes small insertions/deletions from large deletions. We demonstrate CAT-R applications in chemical and genetic screens. First, we evaluate 21 compounds currently in clinical trials which target the DNA damage response. Second, we examine how 417 factors involved in DNA damage response influence the choice between end protection and end resection. Finally, we show that impairing nucleotide excision repair favors error-free repair, providing an alternative way for improving CRISPR/Cas9-based knock-ins. CAT-R is a high-throughput, versatile assay to assess DSB repair choice, which facilitates comprehensive studies of DNA repair and drug efficiency testing. Cells employ different repair pathways to repair DNA double strand breaks. Here, the authors develop a CRISPR/Cas9-dependent method to study choices in DNA repair called the Color Assay Tracing-Repair (CAT-R) which simultaneously measure outcomes of DSB repair via end-protection and end-resection pathways.

2020

Cathepsin S Regulates Antigen Processing and T Cell Activity in Non-Hodgkin Lymphoma

Elena Battistello, Giovanni Ciriello, George Coukos, Elie Charles Eugène Dheilly, Bruno Emanuel Ferreira De Sousa Correia, Natalya Katanayeva, Marco Mina, Elisa Oricchio, Julien Racle, Jessica Sordet-Dessimoz, Stephanie Jocelyne Sungalee, Sarah Wehrle

Genomic alterations in cancer cells can influence the immune system to favor tumor growth. In non-Hodgkin lymphoma, physiological interactions between B cells and the germinal center microenvironment are coopted to sustain cancer cell proliferation. We found that follicular lymphoma patients harbor a recurrent hotspot mutation targeting tyrosine 132 (Y132D) in cathepsin S (CTSS) that enhances protein activity. CTSS regulates antigen processing and CD4+ and CD8+ T cell-mediated immune responses. Loss of CTSS activity reduces lymphoma growth by limiting communication with CD4+ T follicular helper cells while inducing antigen diversification and activation of CD8+ T cells. Overall, our results suggest that CTSS inhibition has non-redundant therapeutic potential to enhance anti-tumor immune responses in indolent and aggressive lymphomas.

2020

EZH2 oncogenic mutations drive epigenetic, transcriptional, and structural changes within chromatin domains

Elena Battistello, Giovanni Ciriello, Maria Christine Donaldson, Kyle Michael Douglass, Natalya Katanayeva, Suliana Manley, Marco Mina, Elisa Oricchio, Timo Henry René Rey, Stephanie Jocelyne Sungalee

Chromatin is organized into topologically associating domains (TADs) enriched in distinct histone marks. In cancer, gain-of-function mutations in the gene encoding the enhancer of zeste homolog 2 protein (EZH2) lead to a genome-wide increase in histone-3 Lys27 trimethylation (H3K27me3) associated with transcriptional repression. However, the effects of these epigenetic changes on the structure and function of chromatin domains have not been explored. Here, we found a functional interplay between TADs and epigenetic and transcriptional changes mediated by mutated EZH2. Altered EZH2 (p.Tyr646* (EZH2Y646X)) led to silencing of entire domains, synergistically inactivating multiple tumor suppressors. Intra-TAD gene silencing was coupled with changes of interactions between gene promoter regions. Notably, gene expression and chromatin interactions were restored by pharmacological inhibition of EZH2Y646X. Our results indicate that EZH2Y646X alters the topology and function of chromatin domains to promote synergistic oncogenic programs.

2019

Conditional Selection of Genomic Alterations Dictates Cancer Evolution and Oncogenic Dependencies

Elena Battistello, Giovanni Ciriello, Titouan Laessle, Marco Mina, Elisa Oricchio, Franck Claude Raynaud, Mohammad Sadegh Saghafinia, Stephanie Jocelyne Sungalee

Cancer evolves through the emergence and selection of molecular alterations. Cancer genome profiling has revealed that specific events are more or less likely to be co-selected, suggesting that the selection of one event depends on the others. However, the nature of these evolutionary dependencies and their impact remain unclear. Here, we designed SELECT, an algorithmic approach to systematically identify evolutionary dependencies from alteration patterns. By analyzing 6,456 genomes from multiple tumor types, we constructed a map of oncogenic dependencies associated with cellular pathways, transcriptional readouts, and therapeutic response. Finally, modeling of cancer evolution shows that alteration dependencies emerge only under conditional selection. These results provide a framework for the design of strategies to predict cancer progression and therapeutic response.

Cell Press2017

Genetic and epigenetic inactivation of SESTRIN1 controls mTORC1 and response to EZH2 inhibition in follicular lymphoma

Elena Battistello, Giovanni Ciriello, Maria Christine Donaldson, Natalya Katanayeva, Elisa Oricchio, Stephanie Jocelyne Sungalee

Follicular lymphoma (FL) is an incurable form of B cell lymphoma. Genomic studies have cataloged common genetic lesions in FL such as translocation t(14;18), frequent losses of chromosome 6q, and mutations in epigenetic regulators such as EZH2 Using a focused genetic screen, we identified SESTRIN1 as a relevant target of the 6q deletion and demonstrate tumor suppression by SESTRIN1 in vivo. Moreover, SESTRIN1 is a direct target of the lymphoma-specific EZH2 gain-of-function mutation (EZH2(Y641X) ). SESTRIN1 inactivation disrupts p53-mediated control of mammalian target of rapamycin complex 1 (mTORC1) and enables mRNA translation under genotoxic stress. SESTRIN1 loss represents an alternative to RRAGC mutations that maintain mTORC1 activity under nutrient starvation. The antitumor efficacy of pharmacological EZH2 inhibition depends on SESTRIN1, indicating that mTORC1 control is a critical function of EZH2 in lymphoma. Conversely, EZH2(Y641X) mutant lymphomas show increased sensitivity to RapaLink-1, a bifunctional mTOR inhibitor. Hence, SESTRIN1 contributes to the genetic and epigenetic control of mTORC1 in lymphoma and influences responses to targeted therapies.

American Association for the Advancement of Science2017