Sass H
Chromosoma. 1980;78(1):33-78. doi: 10.1007/BF00291908.
In order to elucidate the causal relation between RNA synthesis and puffing in polytene chromosomes, salivary gland nuclei and chromosomes from Chironomus tentans and C. pallidivittatus (Diptera, Chironomidae) were isolated in the native state under controlled and optimized conditions. The behavior of the polytene chromatin in vitro as compared to that in vivo was studied morphologically and autoradiographically. It was shown that the absence of cytologically visible puffing does not necessarily indicate transcriptional quiescence. Under suitable conditions all potential puff sites incorporate the radioactive precursor simultaneously. This can be seen in vivo and even more clearly in chromosomes decondensed by 340-400 mM NaCl in vitro. Potential puff sites therefore appear to be permanently equipped with RNA-polymerases, and there is always a basic low level of transcriptive activity. Experimental shrinking of Balbiani rings and other puffs by dimethylsulfoxide (DMSO) or heat shock in vivo, leaves the genes in the collapsed puffs still transcriptionally active, although to a reduced extent. Light optically visible puffing is therefore not a necessary prerequisite for RNA synthesis, while, conversely, RNA synthesis is required for puff formation.
为了阐明多线染色体中RNA合成与胀泡之间的因果关系，在可控且优化的条件下，以天然状态分离了来自细蠓和苍白蠓（双翅目，蠓科）的唾液腺细胞核和染色体。从形态学和放射自显影方面研究了多线染色质在体外与体内的行为。结果表明，细胞学上可见胀泡的缺失并不一定表明转录静止。在合适的条件下，所有潜在的胀泡位点会同时掺入放射性前体。这在体内可见，在体外经340 - 400 mM NaCl解聚的染色体中看得更清楚。因此，潜在的胀泡位点似乎始终配备有RNA聚合酶，并且始终存在基本的低水平转录活性。在体内通过二甲基亚砜（DMSO）或热休克对巴尔比亚尼环和其他胀泡进行实验性收缩，尽管程度有所降低，但塌陷胀泡中的基因仍具有转录活性。因此，光学上可见的胀泡并不是RNA合成的必要前提条件，相反，胀泡形成需要RNA合成。
