Pannekoek H, Noordermeer I, van de Putte P
J Bacteriol. 1979 Jul;139(1):48-53. doi: 10.1128/jb.139.1.48-53.1979.
Recombinant plasmid pNP5, consisting of plasmid pMB9 on which the uvrB gene is cloned, fully complements for the defects due to chromosomal uvrB mutations in the presence of the amber suppressor sup-6 or supF. Correndonuclease II activity was also completely restored in in UvrB strains containing both plasmid pNP5 and amber suppressor sup-6, as compared with the parental UvrB+ strain. It is shown that the amber mutation which interferes with the expression of the cloned uvrB gene is located outside this gene. Apparently, the amber mutation exerts a polar effect on uvrB expression that is relieved by sup-6 or supF. Introduction of a rho mutation into suppressor-free UvrB strains, harboring pNP5, did not relieve the polarity caused by the amber mutation.
重组质粒pNP5由克隆有uvrB基因的质粒pMB9组成，在琥珀抑制基因sup-6或supF存在的情况下，它能完全弥补染色体uvrB突变所导致的缺陷。与亲本UvrB+菌株相比，在同时含有质粒pNP5和琥珀抑制基因sup-6的UvrB菌株中，核酸外切酶II的活性也完全恢复。结果表明，干扰克隆的uvrB基因表达的琥珀突变位于该基因之外。显然，琥珀突变对uvrB表达产生了极性效应，而sup-6或supF可缓解这种效应。将rho突变引入携带pNP5的无抑制基因的UvrB菌株中，并不能缓解由琥珀突变引起的极性效应。
