Epigenetic rewriting at centromeric DNA repeats leads to increased chromatin accessibility and chromosomal instability

Abstract Background Centromeric regions of human chromosomes contain large numbers of tandemly repeated α-satellite sequences. These sequences are covered with constitutive heterochromatin which is enriched in trimethylation of histone H3 on lysine 9 (H3K9me3). Although well studied using artificial chromosomes and global perturbations, the contribution of this epigenetic mark to chromatin structure and genome stability remains poorly known in a more natural context. Results Using transcriptional activator-like effectors (TALEs) fused to a histone lysine demethylase (KDM4B), we were able to reduce the level of H3K9me3 on the α-satellites repeats of human chromosome 7. We show that the removal of H3K9me3 affects chromatin structure by increasing the accessibility of DNA repeats to the TALE protein. Tethering TALE-demethylase to centromeric repeats impairs the recruitment of HP1α and proteins of Chromosomal Passenger Complex (CPC) on this specific centromere without affecting CENP-A loading. Finally, the epigenetic re-writing by the TALE-KDM4B affects specifically the stability of chromosome 7 upon mitosis, highlighting the importance of H3K9me3 in centromere integrity and chromosome stability, mediated by the recruitment of HP1α and the CPC. Conclusion Our cellular model allows to demonstrate the direct role of pericentromeric H3K9me3 epigenetic mark on centromere integrity and function in a natural context and opens interesting possibilities for further studies regarding the role of the H3K9me3 mark.

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Epigenetic dysregulation from chromosomal transit in micronuclei

10.1101/2022.01.12.475944 ◽

2022 ◽

Author(s):

Albert Agustinus ◽

Ramya Raviram ◽

Bhargavi Dameracharla ◽

Jens Luebeck ◽

Stephanie Stransky ◽

...

Keyword(s):

Chromosomal Instability ◽

Chromatin Accessibility ◽

Epigenetic Alterations ◽

Copy Number Alterations ◽

Mitotic Chromosomes ◽

Post Translational Modifications ◽

Positional Bias ◽

Histone Ptms ◽

Mitotic Abnormalities ◽

Intergenic Regions

Chromosomal instability (CIN) and epigenetic alterations are characteristics of advanced and metastatic cancers [1-4], yet whether they are mechanistically linked is unknown. Here we show that missegregation of mitotic chromosomes, their sequestration in micronuclei [5, 6], and subsequent micronuclear envelope rupture [7] profoundly disrupt normal histone post-translational modifications (PTMs), a phenomenon conserved across humans and mice as well as cancer and non-transformed cells. Some of the changes to histone PTMs occur due to micronuclear envelope rupture whereas others are inherited from mitotic abnormalities prior to micronucleus formation. Using orthogonal techniques, we show that micronuclei exhibit extensive differences in chromatin accessibility with a strong positional bias between promoters and distal or intergenic regions. Finally, we show that inducing CIN engenders widespread epigenetic dysregulation and that chromosomes which transit in micronuclei experience durable abnormalities in their accessibility long after they have been reincorporated into the primary nucleus. Thus, in addition to genomic copy number alterations, CIN can serve as a vehicle for epigenetic reprogramming and heterogeneity in cancer.

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Heat Shock Affects Mitotic Segregation of Human Chromosomes Bound to Stress-Induced Satellite III RNAs

International Journal of Molecular Sciences ◽

10.3390/ijms21082812 ◽

2020 ◽

Vol 21 (8) ◽

pp. 2812

Author(s):

Manuela Giordano ◽

Lucia Infantino ◽

Marco Biggiogera ◽

Alessandra Montecucco ◽

Giuseppe Biamonti

Keyword(s):

Heat Shock ◽

Chromosome Segregation ◽

Small Rnas ◽

Chromosomal Instability ◽

Chromosome 9 ◽

Dna Repeats ◽

Human Chromosomes ◽

Chromosome Behavior ◽

Argonaute 2 ◽

Transcription Sites

Heat shock activates the transcription of arrays of Satellite III (SatIII) DNA repeats in the pericentromeric heterochromatic domains of specific human chromosomes, the longest of which is on chromosome 9. Long non-coding SatIII RNAs remain associated with transcription sites where they form nuclear stress bodies or nSBs. The biology of SatIII RNAs is still poorly understood. Here, we show that SatIII RNAs and nSBs are detectable up to four days after thermal stress and are linked to defects in chromosome behavior during mitosis. Heat shock perturbs the execution of mitosis. Cells reaching mitosis during the first 3 h of recovery accumulate in pro-metaphase. During the ensuing 48 h, this block is no longer detectable; however, a significant fraction of mitoses shows chromosome segregation defects. Notably, most of lagging chromosomes and chromosomal bridges are bound to nSBs and contain arrays of SatIII DNA. Disappearance of mitotic defects at the end of day 2 coincides with the processing of long non-coding SatIII RNAs into a ladder of small RNAs associated with chromatin and ranging in size from 25 to 75 nt. The production of these molecules does not rely on DICER and Argonaute 2 components of the RNA interference apparatus. Thus, massive transcription of SatIII DNA may contribute to chromosomal instability.

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Epigenetic rewriting at centromeric DNA repeats leads to increased chromatin accessibility and chromosomal instability

10.1101/2021.02.22.432244 ◽

2021 ◽

Author(s):

Sheldon Decombe ◽

François Loll ◽

Laura Caccianini ◽

Kévin Affannoukoué ◽

Ignacio Izeddin ◽

...

Keyword(s):

Chromatin Structure ◽

Genome Stability ◽

Chromatin Accessibility ◽

Chromosome 7 ◽

Epigenetic Mark ◽

Dna Repeats ◽

Artificial Chromosomes ◽

Chromosomal Passenger ◽

The Stability ◽

Lysine Demethylase

AbstractCentromeric regions of human chromosomes contain large numbers of tandemly repeated α-satellite sequences. These sequences are covered with constitutive heterochromatin which is enriched in trimethylation of histone H3 on lysine 9 (H3K9me3). Although well studied using artificial chromosomes and global perturbations, the contribution of this epigenetic mark to chromatin structure and genome stability remains poorly known in a more natural context. Using transcriptional activator-like effectors (TALEs) fused to a histone lysine demethylase (JMJD2B), we were able to reduce the level of H3K9me3 on the α-satellites repeats of human chromosome 7. We show that the removal of H3K9me3 affects chromatin structure by increasing the accessibility of DNA repeats to the TALE protein. Tethering TALE-demethylase to centromeric repeats impairs the recruitment of HP1α and proteins of Chromosomal Passenger Complex (CPC) on this specific centromere. Finally, the epigenetic re-writing by the TALE-JMJD2B affects specifically the stability of chromosome 7 upon mitosis, highlighting the importance of H3K9me3 in centromere integrity and chromosome stability, mediated by the recruitment of HP1α and the CPC.

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A Tale of Two Colons and Two Cancers

Swiss Surgery ◽

10.1024/1023-9332.9.1.3 ◽

2003 ◽

Vol 9 (1) ◽

pp. 3-7 ◽

Cited By ~ 5

Author(s):

Gervaz ◽

Bühler ◽

Scheiwiller ◽

Morel

Keyword(s):

Colorectal Cancer ◽

Colon Cancer ◽

Adjuvant Chemotherapy ◽

Splenic Flexure ◽

Chromosomal Instability ◽

Proximal Colon ◽

Colorectal Carcinogenesis ◽

Physiological Data ◽

Central Hypothesis ◽

Group Stratification

The central hypothesis explored in this paper is that colorectal cancer (CRC) is a heterogeneous disease. The initial clue to this heterogeneity was provided by genetic findings; however, embryological and physiological data had previously been gathered, showing that proximal (in relation to the splenic flexure) and distal parts of the colon represent distinct entities. Molecular biologists have identified two distinct pathways, microsatellite instability (MSI) and chromosomal instability (CIN), which are involved in CRC progression. In summary, there may be not one, but two colons and two types of colorectal carcinogenesis, with distinct clinical outcome. The implications for the clinicians are two-folds; 1) tumors originating from the proximal colon have a better prognosis due to a high percentage of MSI-positive lesions; and 2) location of the neoplasm in reference to the splenic flexure should be documented before group stratification in future trials of adjuvant chemotherapy in patients with stage II and III colon cancer.

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