Showing papers by "Jekaterina Erenpreisa published in 2020"

"Mitotic Slippage" and Extranuclear DNA in Cancer Chemoresistance: A Focus on Telomeres

Abstract: Mitotic slippage (MS), the incomplete mitosis that results in a doubled genome in interphase, is a typical response of TP53-mutant tumors resistant to genotoxic therapy. These polyploidized cells display premature senescence and sort the damaged DNA into the cytoplasm. In this study, we explored MS in the MDA-MB-231 cell line treated with doxorubicin (DOX). We found selective release into the cytoplasm of telomere fragments enriched in telomerase reverse transcriptase (hTERT), telomere capping protein TRF2, and DNA double-strand breaks marked by γH2AX, in association with ubiquitin-binding protein SQSTM1/p62. This occurs along with the alternative lengthening of telomeres (ALT) and DNA repair by homologous recombination (HR) in the nuclear promyelocytic leukemia (PML) bodies. The cells in repeated MS cycles activate meiotic genes and display holocentric chromosomes characteristic for inverted meiosis (IM). These giant cells acquire an amoeboid phenotype and finally bud the depolyploidized progeny, restarting the mitotic cycling. We suggest the reversible conversion of the telomerase-driven telomere maintenance into ALT coupled with IM at the sub-telomere breakage sites introduced by meiotic nuclease SPO11. All three MS mechanisms converging at telomeres recapitulate the amoeba-like agamic life-cycle, decreasing the mutagenic load and enabling the recovery of recombined, reduced progeny for return into the mitotic cycle.

Phylostratic Shift of Whole-Genome Duplications in Normal Mammalian Tissues towards Unicellularity Is Driven by Developmental Bivalent Genes and Reveals a Link to Cancer.

Abstract: Tumours were recently revealed to undergo a phylostratic and phenotypic shift to unicellularity. As well, aggressive tumours are characterized by an increased proportion of polyploid cells. In order to investigate a possible shared causation of these two features, we performed a comparative phylostratigraphic analysis of ploidy-related genes, obtained from transcriptomic data for polyploid and diploid human and mouse tissues using pairwise cross-species transcriptome comparison and principal component analysis. Our results indicate that polyploidy shifts the evolutionary age balance of the expressed genes from the late metazoan phylostrata towards the upregulation of unicellular and early metazoan phylostrata. The up-regulation of unicellular metabolic and drug-resistance pathways and the downregulation of pathways related to circadian clock were identified. This evolutionary shift was associated with the enrichment of ploidy with bivalent genes (p < 10-16). The protein interactome of activated bivalent genes revealed the increase of the connectivity of unicellulars and (early) multicellulars, while circadian regulators were depressed. The mutual polyploidy-c-MYC-bivalent genes-associated protein network was organized by gene-hubs engaged in both embryonic development and metastatic cancer including driver (proto)-oncogenes of viral origin. Our data suggest that, in cancer, the atavistic shift goes hand-in-hand with polyploidy and is driven by epigenetic mechanisms impinging on development-related bivalent genes.

The Role of the Meiotic Component in Reproduction of B-RAF-Mutated Melanoma: A Review and “Brainstorming” Session

Abstract: The ectopic expression of cancer testis (CT) antigens and classic meiotic genes is characteristic and a hallmark of poor prognosis of melanoma disease. Here the potential mechanisms of meiotic influence on the cell and life cycle of malignant melanoma are reviewed in the genetic, epigenetic, and evolutionary aspects. The involved mutant B-RAF and N-RAS-induced senescence may be reversed by reprogramming, with stemness linked to meiotic landscape, possibly induced by DNA double-strand breaks at the mutual telomere hot spots. The induced by senescence mitotic slippage (reset of interphase from arrested metaphase) and resulting polyploidy trigger the meiotic ploidy cycle to function for effective DNA recombination repair, genome reduction, and escape of survivors, which enter the mitotic cycle again. The aberrant meiotic pathway in cancer is reviewed in the ancestral asexual variants; inverted meiosis is possible. The conundrum of cancer aneuploidy paradox, selection of fit clones, and the Muller’s Ratchet of inevitable accumulation of harmful mutations is discussed. The bioinformatic study of the densely connected protein interaction network of CT antigen expressed genes revealed the melanomagenesis attractor composed of PRAME and small MAGEA group in primary tumors as compared with B-RAF-mutant nevi, restructured stemness network; invasive melanoma further displays the leading role of SPANX CT antigen group; meiotic genes are expressed in all three tissue cohorts.

Early Critical Phase Transitions of Pericentromere-Associated Domains in MCF-7 Breast Cancer Cells Committed to Differentiation by Heregulin

Abstract: Finding out how cells with the same genome change fates in differentiation commitment is a challenge of biology. We used MCF-7 breast cancer cells treated with the ErbB2 ligand heregulin (HRG), which induces differentiation, to address if and how the constitutive pericentromere-associated domains (PADs) may be involved in this process. PAD-specific repressive heterochromatin (H3K9me3) and active euchromatin (H3K4me3) marking, centromere (CENPA) labelling, qPCR, acridine-orange-DNA structural test, and microscopic image analysis were applied. We found a two-step DNA unfolding, at 15-20 min and 60 min after HRG treatment, coinciding with bi-phasic activation of the early response genes (c-FOS family) and two steps of critical phase transition which were revealed in transcriptome studies. In control, the distribution of PAD number and size displays a power-law scaling with a boundary at the nucleolus. PADs’ clustering correlates with centromere numbers. 15 min after HRG treatment, the unravelling of PADs occurs, coinciding with the first step of euchromatin unfolding. The second step is associated with transcription of long-non-coding-RNA from satellite III DNA. We hypothesize that splitting of the PAD clusters under the critical size threshold of the silencing domain abrupts position effect variegation. It allows the first genome transcription avalanche to occur, starting differentiation commitment.