- The Scientist News & Opinion 12/10/12
Conserved Chromatin? Re: R. Ammar et al., “Chromatin is an ancient innovation conserved between Archaea and Eukarya,” eLife, 1:e00078, 2012.
Excerpt: “If the primary role for chromatin is not packaging, it might instead be to regulate gene expression,” Nislow said.
At the advent of sexual reproduction, a type of epigenetic imprinting occurs in species as diverse as yeast, Drosophila, mice, and humans. This epigenetic imprinting is based upon small DNA-binding proteins called “chromo domain” proteins, e.g., polycomb. These proteins affect chromatin structure, often in telomeric regions, and thereby affect transcription and silencing of various genes. Small intranuclear proteins also participate in generating alternative splicing techniques of pre-mRNA and, by this mechanism, contribute to sexual differentiation in at least two species, Drosophila melanogaster and Caenorhabditis elegans. That similar proteins perform functions in humans suggests the possibility that some human sex differences may arise from alternative splicings of otherwise identical genes.
The new information on conserved chromatin suggests it makes sense to move backwards across the continuum of adaptive evolution and attempt to determine whether the conservation of chromatin between Archeea and Eukarya is nutrient chemical-dependent and pheromone-controlled, since this appears to be the case via the epigenetic effects of nutrient chemicals and pheromones on all life (e.g., as we know it). Nevertheless, the bottom-up epigenetic effects of nutrient chemicals on speciation that are concurrently controlled by the top-down epigenetic effects of pheromones on reproduction challenges those who might rather attempt to-explain away the conserved molecular biology of adaptive evolution via random mutations theory. I don’t see how any existing theory could explain cause and effect exemplified by complex systems biology in the simplest of organisms with their “ancient innovation” of conserved chromatin. Is there a model of adaptively evolved Natural Selection and Sexual Selection for that?
See also: The activity-dependent histone variant H2BE modulates the life span of olfactory neurons
Stephen W Santoro and Catherine Dulac (2012) “These findings uncover a novel mechanism by which the sensory experience of a neuron is recorded within its chromatin to affect its transcriptional program and longevity.”