Chromatin and epigenetics: current biophysical views

Recent advances in high-throughput sequencing experiments and their theoretical descriptions have determined fast dynamics of the "chromatin and epigenetics" field, with new concepts appearing at high rate. This field includes but is not limited to the study of DNA-protein-RNA interactions, chromatin packing properties at different scales, regulation of gene expression and protein trafficking in the cell nucleus, binding site search in the crowded chromatin environment and modulation of physical interactions by covalent chemical modifications of the binding partners. The current special issue does not pretend for the full coverage of the field, but it rather aims to capture its development and provide a snapshot of the most recent concepts and approaches. Eighteen open-access articles comprising this issue provide a delicate balance between current theoretical and experimental biophysical approaches to uncover chromatin structure and understand epigenetic regulation, allowing free flow of new ideas and preliminary results

Vertebrate Genome Size and the Impact of Transposable Elements in Genome Evolution

In eukaryotes, the haploid DNA content (C-value) varies widely across lineages without an apparent correlation with the complexity of organisms. This incongruity has been called the C-value paradox and has been solved by demonstrating that not all DNA is constituted by genes but, on the contrary,most of it ismade up of repetitive DNA. In vertebrates, the increasing number of sequenced genomes has shown that differences in genome size between lineages are ascribable to a variation in transposon content. These mobile elements, previously perceived as “junk DNA” or “selfish DNA,” are now recognized as the major players in shaping genomes. During vertebrate evolution, transposable elements have been repeatedly co-opted and exapted to generate regulatory sequences, coding exons, or entirely new genes that lead to evolutionary advantages for the host. Moreover, transposable elements are also responsible for substantial rearrangements such as insertions, deletions, inversions, and duplications potentially associated with, or following, speciation events