UTILIZING SPERMATOZOA WITH THE HIGHEST GENOMIC INTEGRITY ENHANCES ICSI OUTCOME

AbstractThe poly(ADP-ribose) polymerase, PARP1, plays a key role in maintaining genomic integrity by detecting DNA damage and mediating repair. γH2A.X is the primary histone marker for DNA double-strand breaks and PARP1 localizes to H2A.X-enriched chromatin damage sites, but the basis for this association is not clear. We characterize the kinetics of PARP1 binding to a variety of nucleosomes harbouring DNA double-strand breaks, which reveal that PARP1 associates faster with (γ)H2A.X- versus H2A-nucleosomes, resulting in a higher affinity for the former, which is maximal for γH2A.X-nucleosome that is also the activator eliciting the greatest poly-ADP-ribosylation catalytic efficiency. The enhanced activities with γH2A.X-nucleosome coincide with increased accessibility of the DNA termini resulting from the H2A.X-Ser139 phosphorylation. Indeed, H2A- and (γ)H2A.X-nucleosomes have distinct stability characteristics, which are rationalized by mutational analysis and (γ)H2A.X-nucleosome core crystal structures. This suggests that the γH2A.X epigenetic marker directly facilitates DNA repair by stabilizing PARP1 association and promoting catalysis.

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Protecting genomic integrity in somatic cells and embryonic stem cells

Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis ◽

10.1016/j.mrfmmm.2006.06.006 ◽

2007 ◽

Vol 614 (1-2) ◽

pp. 48-55 ◽

Cited By ~ 80

Author(s):

Y. Hong ◽

R.B. Cervantes ◽

E. Tichy ◽

J.A. Tischfield ◽

P.J. Stambrook

Keyword(s):

Stem Cells ◽

Embryonic Stem Cells ◽

Somatic Cells ◽

Embryonic Stem ◽

Genomic Integrity

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Novel Roles for the Sirtuin Deacylase SIRT5 in Normal Physiology and in Cancer

Innovation in Aging ◽

10.1093/geroni/igaa057.2652 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

pp. 741-741

Author(s):

David Lombard

Keyword(s):

Mitochondrial Matrix ◽

Genomic Integrity ◽

Biological Functions ◽

Protein Targets ◽

Post Translational Modifications ◽

Catalytic Activities ◽

Cellular Processes ◽

Specific Cancer ◽

Cancer Types ◽

Chromatin Biology

Abstract Sirtuins are NAD+-dependent deacylases that regulate diverse cellular processes such as metabolic homeostasis and genomic integrity. Mammals possess seven sirtuin family members, SIRT1-SIRT7, that display diverse subcellular localization patterns, catalytic activities, protein targets, and biological functions. Three sirtuins, SIRT3, SIRT4, and SIRT5, are primarily located in the mitochondrial matrix. SIRT5 is a very inefficient deacetylase, instead removing negatively charged post-translational modifications (succinyl, glutaryl, and malonyl groups) from lysines of its target proteins, in mitochondria and throughout the cell. SIRT5 plays only modest known roles in normal physiology, with its major functions occurring in the heart under stress conditions. In contrast, in specific cancer types, including melanoma, we have identified a major pro-survival role for SIRT5. We have traced this function of SIRT5 to novel roles for this protein in regulating chromatin biology. New insights into mechanisms of SIRT5 action in cancer, and in normal myocardium, will be discussed.

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Single bacterial resolvases first exploit, then constrain intrinsic dynamics of the Holliday junction to direct recombination

Nucleic Acids Research ◽

10.1093/nar/gkab096 ◽

2021 ◽

Author(s):

Sujay Ray ◽

Nibedita Pal ◽

Nils G Walter

Keyword(s):

Cluster Analysis ◽

Homologous Recombination ◽

Single Molecule ◽

Holliday Junction ◽

Energetic Cost ◽

Genomic Integrity ◽

Dna Molecules ◽

Single Molecule Fluorescence ◽

And Cluster Analysis ◽

Fluorescence Observation

Abstract Homologous recombination forms and resolves an entangled DNA Holliday Junction (HJ) crucial for achieving genetic reshuffling and genome repair. To maintain genomic integrity, specialized resolvase enzymes cleave the entangled DNA into two discrete DNA molecules. However, it is unclear how two similar stacking isomers are distinguished, and how a cognate sequence is found and recognized to achieve accurate recombination. We here use single-molecule fluorescence observation and cluster analysis to examine how prototypic bacterial resolvase RuvC singles out two of the four HJ strands and achieves sequence-specific cleavage. We find that RuvC first exploits, then constrains the dynamics of intrinsic HJ isomer exchange at a sampled branch position to direct cleavage toward the catalytically competent HJ conformation and sequence, thus controlling recombination output at minimal energetic cost. Our model of rapid DNA scanning followed by ‘snap-locking’ of a cognate sequence is strikingly consistent with the conformational proofreading of other DNA-modifying enzymes.

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