Heterochromatin is a key architectural feature of eukaryotic chromosomes, which endows particular genomic domains with specific functional properties. The capacity of heterochromatin to restrain the activity of mobile elements, isolate DNA repair in repetitive regions and ensure accurate chromosome segregation is crucial for maintaining genomic stability. Nucleosomes at heterochromatin regions display histone post-translational modifications that contribute to developmental regulation by restricting lineage-specific gene expression. The mechanisms of heterochromatin establishment and of heterochromatin maintenance are separable and involve the ability of sequence-specific factors bound to nascent transcripts to recruit chromatin-modifying enzymes. Heterochromatin can spread along the chromatin from nucleation sites. The propensity of heterochromatin to promote its own spreading and inheritance is counteracted by inhibitory factors. Because of its importance for chromosome function, heterochromatin has key roles in the pathogenesis of various human diseases. In this Review, we discuss conserved principles of heterochromatin formation and function using selected examples from studies of a range of eukaryotes, from yeast to human, with an emphasis on insights obtained from unicellular model organisms.

异染色质是真核染色体的一个关键结构特征，它赋予特定的基因组域特定的功能特性。异染色质抑制移动元件的活性、隔离重复区域中的 DNA 修复并确保准确的染色体分离的能力对于维持基因组稳定性至关重要。异染色质区域的核小体显示组蛋白翻译后修饰，通过限制谱系特异性基因表达促进发育调控。异染色质建立和异染色质维持的机制是可分离的，涉及与新生转录本结合的序列特异性因子募集染色质修饰酶的能力。异染色质可以从成核位点沿着染色质扩散。异染色质促进其自身传播和遗传的倾向被抑制因素抵消。由于其对染色体功能的重要性，异染色质在各种人类疾病的发病机制中起着关键作用。在这篇综述中，我们使用从酵母到人类等一系列真核生物的研究中选定的例子来讨论异染色质形成和功能的保守原则，重点是从单细胞模式生物中获得的见解。