Brown C J
Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
Semin Reprod Med. 2001 Jun;19(2):125-32. doi: 10.1055/s-2001-15392.
X chromosome inactivation achieves dosage equivalence for most X-linked genes between the two X chromosomes in females and the single X chromosome in males. In this article the evidence for random inactivation of an X chromosome is reviewed, along with the exceptions that result in nonrandom inactivation. Another exception to X chromosome inactivation is the presence of genes that escape inactivation and are expressed from both the active and inactive X chromosomes. The phenotypic consequences of such expression from the inactive X chromosome are discussed. The major players in the process of inactivation are presented. Initiation of inactivation requires the functional RNA, XIST, and the subsequent stable inactivation of the X chromosome relies upon the recruitment of many other factors, the majority of which are generally associated with heterochromatin.
X染色体失活使雌性两条X染色体和雄性单条X染色体上的大多数X连锁基因实现剂量均等。本文回顾了X染色体随机失活的证据以及导致非随机失活的例外情况。X染色体失活的另一个例外是存在逃避失活并从活性和非活性X染色体上均表达的基因。讨论了从非活性X染色体上这种表达的表型后果。介绍了失活过程中的主要参与者。失活的起始需要功能性RNA XIST，随后X染色体的稳定失活依赖于许多其他因子的募集，其中大多数通常与异染色质相关。
