Chemical modifications to these histones can change the expression of genes, making them more available for expression or silencing them by compacting the DNA-protein complex. Oddball H3.3 varies from its regular counterpart H3 by only few amino acids.
The research has implications beyond epigenetics. “This study also hints at a fascinating question in biology: How do cells balance the potential evolutionary benefit of mobile elements, such as retrotransposons, with the competing need to silence them so as to maintain the genome?” she says.
My comment: Cells do not balance the ‘potential evolutionary benefit’ of viral microRNAs. The entropic elasticity that links viral microRNAs to pathology is balanced by the anti-entropic epigenetic effect of nutrient-dependent microRNAs. Nutrient-dependent microRNAs link beneficial changes in the microRNA/messenger RNA balance to RNA-mediated amino acid substitutions that differentiate all cell types of all individuals of all genera. The need to control the entropy caused by viruses arises in the context of fixation of the amino acid substitutions via the physiology of reproduction. Fixation is nutrient-dependent and pheromone-controlled in species from microbes to man. Researchers who wonder “How do cells balance the potential evolutionary benefit of mobile elements…” have framed the question in the context of ridiculous theories, and they may need to begin learning about the biologically-based cause and effect manifested in cell type differentiation.
See also: MicroRNAs and the exposome