Radiation and the regulatory landscape of neo2-Darwinism

Epigenetic features in the oyster Crassostrea gigas suggestive of functionally relevant promoter DNA methylation in invertebrates

DNA methylation is evolutionarily conserved. Vertebrates exhibit high, widespread DNA methylation whereas invertebrate genomes are less methylated, predominantly within gene bodies. DNA methylation in invertebrates is associated with transcription level, alternative splicing, and genome evolution, but functional outcomes of DNA methylation remain poorly described in lophotrochozoans. Recent genome-wide approaches improve understanding in distant taxa such as molluscs, where the phylogenetic position, and life traits of Crassostrea gigas make this bivalve an ideal model to study the physiological and evolutionary implications of DNA methylation. We review the literature about DNA methylation in invertebrates and focus on DNA methylation features in the oyster. Indeed, though our MeDIP-seq results confirm predominant intragenic methylation, the profiles depend on the oyster's developmental and reproductive stage. We discuss the perspective that oyster DNA methylation could be biased toward the 5'-end of some genes, depending on physiological status, suggesting important functional outcomes of putative promoter methylation from cell differentiation during early development to sustained adaptation of the species to the environment.

Histone deacetylase inhibitor and demethylating agent chromatin compaction and the radiation response by cancer cells

It now appears that epigenetics plays a central role in transformation, both in vitro and in vivo. The expression and regulation of DNA methylation and the subsequent chromatin structure are significantly altered in tumor cells, suggesting a direct role in the process of in vivo cellular transformation. If epigenetics and posttranslational modifications of histones play a role in transformation, then it seems logical that the genes regulating chromatin compaction may also be molecular targets and markers in profiling tumor cell resistance. Local remodeling of chromatin is a key step in the regulation of gene expression, and altering the expression of these genes might also favorably alter how tumor cells respond to anticancer agents. Several new agents that alter chromatin compaction, either methyltransferase or histone deacetylases inhibitors, are progressing through clinical trials and have shown promising preclinical interactions when combined with radiation. In this review, we discuss the potential for histone deacetylases inhibitors as radiosensitizing agents.