Martin R, Hearn M, Jenny P, Gallant J
Department of Genetics, University of Washington, Seattle 98195.
Mol Gen Genet. 1988 Jul;213(1):144-9. doi: 10.1007/BF00333411.
We have compared the competition between strong or weak suppressor tRNAs and translational release factors (RF) at nonsense codons in the lacI gene of Escherichia coli. Using the F'lacIZ fusions developed by Miller and coworkers, UAG, UAA, and UGA codons at positions 189 and 220 were efficiently suppressed by plasmid-borne tRNA(trp) suppressors cognate to each nonsense triplet. Introduction of a compatible RF 1 plasmid competed at UAG and UAA but not UGA codons. An RF2 expressing plasmid competed at UAA and UGA but had little effect at UAG. Release factor competition against weak suppressors was measured using combinations of noncognate suppressors and nonsense codons. In each case, release factor plasmids behaved identically towards poorly suppressed codons as they did when the same codons were efficiently suppressed. The implications for these studies on the role of release factors in nonsense suppression context effects are discussed.
我们比较了强或弱抑制性tRNA与翻译释放因子（RF）在大肠杆菌lacI基因无义密码子处的竞争情况。利用米勒及其同事构建的F'lacIZ融合体，位于189和220位的UAG、UAA和UGA密码子能被与各无义三联体同源的质粒携带的tRNA（trp）抑制子有效抑制。引入一个相容的RF1质粒会在UAG和UAA密码子处产生竞争，但在UGA密码子处则不会。一个表达RF2的质粒会在UAA和UGA密码子处产生竞争，但对UAG密码子影响很小。使用非同源抑制子和无义密码子的组合来测定释放因子对弱抑制子的竞争情况。在每种情况下，释放因子质粒对抑制效果较差的密码子的作用，与对相同密码子被有效抑制时的作用相同。文中讨论了这些研究对释放因子在无义抑制背景效应中作用的意义。
