Dillon Niall, Festenstein Richard
Gene Regulation and Chromatin Group, MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College, Hammersmith Campus, Du Cane Road, London, UK W12 0NN.
Trends Genet. 2002 May;18(5):252-8. doi: 10.1016/s0168-9525(02)02648-3.
Heterochromatin mediates many diverse functions in the cell nucleus, including centromere function, gene silencing and nuclear organization. The condensed structure of pericentromeric heterochromatin is associated with the presence of a regular arrangement of nucleosomes, which might be due in part to the underlying sequence of the satellite repeats. Recent studies identified methylation of the histone H3 tail as an epigenetic mark that affects acetylation and phosphorylation of histone tail residues and also acts as a recognition signal for binding of heterochromatin protein 1 (HP1). The decision to silence or activate heterochromatic genes appears to be the result of a balance between negative factors that promote the formation of condensed higher-order chromatin structure, and positively acting transcription factors that bind to regulatory sequences and activate gene expression.
异染色质介导细胞核内多种不同的功能，包括着丝粒功能、基因沉默和细胞核组织。着丝粒周围异染色质的浓缩结构与核小体的规则排列有关，这可能部分归因于卫星重复序列的潜在序列。最近的研究发现组蛋白H3尾巴的甲基化是一种表观遗传标记，它影响组蛋白尾巴残基的乙酰化和磷酸化，并且还作为异染色质蛋白1（HP1）结合的识别信号。沉默或激活异染色质基因的决定似乎是促进浓缩的高阶染色质结构形成的负性因子与结合调控序列并激活基因表达的正性作用转录因子之间平衡的结果。
