RNAs (ncRNA) and/or protein gene products. In this circumstance, these macromolecules act to alter chromatin structure, transcription, RNA splicing, editing, and translation—ultimately shaping gene expression.[13] The best-known example of epigenetic alteration of gene expression by RNA is the inactivation of secondary X-chromosomes in mammalian females.[13] Recent research has also identified a fourth epigenetic mechanism. Prions are remarkably stable proteins that have the capacity to alter protein folding by acting as conformational templates. Prions can then act epigenetically by “sidestepping” nucleic acid metabolism altogether to alter protein conformation and therefore structure and function in the cell.[14] While epigenetic prions have yet to be demonstrated in humans, research has demonstrated that prion proteins may play an important role in yeast evolution.[15]
