Fluck M M, Epstein R H
Mol Gen Genet. 1980;177(4):615-27. doi: 10.1007/BF00272672.
Secondary mutations which increase the efficiency of suppression of nonsense mutations in the rIIB cistron of bacteriophage T4 have been isolated. These secondary mutations, called context mutations, map at sites very close to the nonsense codon, possibly on the promotor distal side. In context-nonsense double mutants, the amount of suppressed gene product is increased approximately 10-fold. The context mutations examined can act on the UAA (ochre) nonsense allele as well as on the UAG (amber) nonsense allele at a given site. These context mutations affect all suppression mechanisms analyzed (genetic suppressors, 5-fluorouracil suppression and spontaneous suppression). We suggest that context mutations affect information which is significant to the termination of polypeptide chains. According to our view, context mutations change the immediate neighborhood of nonsense mutations and so reduce the degree of resemblance to the sequences normally used for the termination of translation.
已分离出能提高噬菌体T4 rIIB顺反子中无义突变抑制效率的二级突变。这些二级突变称为上下文突变，位于非常靠近无义密码子的位点，可能在启动子远端一侧。在上下文-无义双突变体中，被抑制的基因产物量增加约10倍。所检测的上下文突变可作用于给定位点的UAA（赭石）无义等位基因以及UAG（琥珀）无义等位基因。这些上下文突变影响所有分析的抑制机制（遗传抑制子、5-氟尿嘧啶抑制和自发抑制）。我们认为，上下文突变影响对多肽链终止至关重要的信息。根据我们的观点，上下文突变改变了无义突变的紧邻区域，从而降低了与通常用于翻译终止的序列的相似程度。
