Yao Jie, Ardehali M Behfar, Fecko Christopher J, Webb Watt W, Lis John T
School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
Mol Cell. 2007 Dec 28;28(6):978-90. doi: 10.1016/j.molcel.2007.10.017.
Transcription activation causes dramatic changes in a gene's compaction and macromolecular associations and, in some cases, triggers the translocation of the gene to a nuclear substructure. Here, we evaluate the location, movement, and transcriptional dynamics of Drosophila heat shock (HS) genes both by two-photon microscopy in live polytene nuclei and by FISH in diploid nuclei. The different HS loci occupy separate nuclear positions. Although these loci decondense upon HS, they do not undergo a detectable net translocation nor are they preferentially localized to the nuclear periphery or interior. Additionally, fluorescence recovery after photobleaching reveals that, shortly after HS, newly recruited RNA polymerase II (Pol II) enters elongation via an "efficient entry" mode, which is followed by the progressive establishment of transcription "compartments" at Hsp70 loci where concentrated Pol II is used in a "local recycling" mode. Pol II at highly transcribed developmental loci exhibits dynamics resembling combinations of these Hsp70 transcription modes.
转录激活会导致基因的紧密程度和大分子关联发生显著变化，在某些情况下，还会引发基因向核亚结构的转位。在这里，我们通过在活的多线核中进行双光子显微镜观察以及在二倍体核中进行荧光原位杂交（FISH），来评估果蝇热休克（HS）基因的位置、移动和转录动态。不同的HS基因座占据着独立的核位置。尽管这些基因座在热休克时会解聚，但它们并未发生可检测到的净转位，也没有优先定位于核周或核内部。此外，光漂白后的荧光恢复显示，热休克后不久，新招募的RNA聚合酶II（Pol II）通过“高效进入”模式进入延伸阶段，随后在Hsp70基因座逐渐形成转录“区室”，在那里浓缩的Pol II以“局部循环”模式被使用。在高度转录的发育基因座上的Pol II表现出类似于这些Hsp70转录模式组合的动态变化。
