Talbert Paul B, Henikoff Steven
Howard Hughes Medical Institute, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, Washington 98109, USA.
Nat Rev Genet. 2006 Oct;7(10):793-803. doi: 10.1038/nrg1920.
One of the oldest unsolved problems in genetics is the observation that gene silencing can 'spread' along a chromosome. Although spreading has been widely perceived as a process of long-range assembly of heterochromatin proteins, such 'oozing' might not apply in most cases. Rather, long-range silencing seems to be a dynamic process, involving local diffusion of histone-modifying enzymes from source binding sites to low-affinity sites nearby. Discontinuous silencing might reflect looping interactions, whereas the spreading of continuous silencing might be driven by the processive movement of RNA or DNA polymerases. We review the evidence for the spreading of silencing in many contexts and organisms and conclude that multiple mechanisms have evolved that silence genes at a distance.
遗传学中最古老的未解之谜之一是观察到基因沉默能够沿染色体“扩散”。尽管扩散现象一直被广泛认为是异染色质蛋白进行长距离组装的过程，但这种“渗透”在大多数情况下可能并不适用。相反，长距离沉默似乎是一个动态过程，涉及组蛋白修饰酶从源结合位点向附近低亲和力位点的局部扩散。间断性沉默可能反映了环状相互作用，而连续性沉默的扩散可能由RNA或DNA聚合酶的持续性移动所驱动。我们综述了在多种环境和生物体中沉默扩散的证据，并得出结论：已经进化出了多种机制来远距离沉默基因。
