Authors:	Piccinno, Rossana
Title:	The role of class I histone deacetylases in the formation of chromosome translocations
Online publication date:	30-Nov-2022
Year of first publication:	2022
Language:	english
Abstract:	Exposure to DNA damaging agents and failure of safeguarding genome integrity mechanisms could lead to accumulation of DNA Double strands breaks (DSBs) that increase the risk of forming chromosome translocations. Chromosome translocations are low in frequency gene fusions, which could provoke deregulation of gene expression of oncogenes and tumor suppressor genes, and thereby, drive tumorigenesis. Chromosome translocations are the result of a multistep process, which lead to illegitimate fusion of spatially proximal DSBs from different chromosomes. However, because of their rare occurrence and the lack of research efforts in investigating upstream events of DSB illegitimate repair, molecular players and pathways dictating the formation of chromosome translocations are not fully elucidated. For instance, although DSBs and chromosome translocations occur in the context of highly ordered chromatin organization, whether and how chromatin-related functions influence the frequency of chromosome translocations remain unclear. Here, we raised the hypothesis that chromatin-related functions might affect also the propensity of two DSBs to pair within the nucleus and, then, to engage in an illegitimate repair fusion, thereby influencing the frequency of chromosome translocations. To address this, we performed a screening to identify epigenetic inhibitors that influence the frequency of chromosome translocations. We found that Class I HDACs inhibitors act as suppressors of chromosome translocations. In particular, both global loss-of-function experiments and local tethering of HDAC1 in proximity of breakpoints revealed that HDAC1 facilitates the formation of chromosome translocations. To reveal the molecular mechanisms underlying HDAC1-dependent increase in translocation frequency, we have used the DIvA system by which we could monitor changes in chromosome translocation frequencies in correlation with acetylation levels in the vicinity of DSBs-induced via AsiSI endonuslease. Using sBLISS to profile repair kinetics of AsiSI-DSBs genome-wide, we correlated translocation frequency, acetylation levels in the vicinity of induced DSBs and DSB repair rates. However, we found that change in acetylation levels in the vicinity of induced DSBs does not influence the DSB repair kinetics. To dissect DSBs dynamics in cells with global perturbed levels of HDACs we developed a system to spatially and temporally control the formation of DSBs. Since translocating DSBs show higher mobility compared to non-translocating DSBs, we sought to dissect whether DSB-motion properties are influenced by changes on the levels of histone acetylation, in a degree to affect the frequency of translations. We demonstrated that HDACs inhibitors or depletion of HDAC1 lead to retention of histone acetyl marks onto chromatin and provoke decreased mean square displacement compared to control conditions, suggesting that HDAC1-dependent acetylation might facilitate the propensity of a DSB to move faster and synapse with a translocation-partner. Finally, we validated that HDACs inhibition suppresses the occurrence of recurrent oncogenic MLL translocations upon chemotherapeutic treatment with etoposide, without decreasing the cytotoxic effect of TOP2 poison. Together, our results indicate that histone hyper-acetylation due to lack of HDAC1 activity decreases the frequency of chromosome translocations by decreasing DSB mobility.
DDC:	570 Biowissenschaften 570 Life sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 10 Biologie
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-8182
URN:	urn:nbn:de:hebis:77-openscience-64b33dd9-ff23-4a8d-9da9-3d6475bf8a887
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	http://rightsstatements.org/vocab/InC/1.0/
Extent:	164 Seiten ; Illustrationen, Diagramme
Appears in collections:	JGU-Publikationen