Epigenetics refers to changes in phenotype that are not rooted in DNA sequence. This phenomenon has largely been studied in the context of chromatin modification. Yet many epigenetic traits are instead linked to self-perpetuating changes in the individual or collective activity of proteins. Most such proteins are prions (e.g., [PSI⁺], [URE3], [SWI⁺], [MOT3⁺], [MPH1⁺], [LSB⁺], and [GAR⁺]), which have the capacity to adopt at least one conformation that self-templates over long biological timescales. This allows them to serve as protein-based epigenetic elements that are readily broadcast through mitosis and meiosis. In some circumstances, self-templating can fuel disease, but it also permits access to multiple activity states from the same polypeptide and transmission of that information across generations. Ensuing phenotypic changes allow genetically identical cells to express diverse and frequently adaptive phenotypes. Although long thought to be rare, protein-based epigenetic inheritance has now been uncovered in all domains of life.

表观遗传学是指不扎根于DNA序列的表型变化。在染色质修饰的背景下已对该现象进行了广泛的研究。然而，许多表观遗传特性却与蛋白质的个体或集体活性中的自我延续的变化有关。大多数此类蛋白质是病毒（例如[ PSI ⁺ ]，[URE3]，[ SWI ⁺ ]，[ MOT3 ⁺ ]，[ MPH1 ⁺ ]，[ LSB ⁺ ]和[ GAR ⁺]），它们有能力采用至少一种在较长的生物学时间尺度上可以自我模板化的构象。这使它们可以作为基于蛋白质的表观遗传元素，可以通过有丝分裂和减数分裂容易地传播。在某些情况下，自我模板化可以助长疾病，但它也允许从同一多肽访问多个活性状态，并跨代传递该信息。随后的表型改变使遗传上相同的细胞能够表达多种多样且经常具有适应性的表型。尽管长期以来一直被认为是罕见的，但是基于蛋白质的表观遗传继承现在已经在生活的所有领域中被发现。