Maley F, Chu F K, Maley G F
Wadsworth Center for Laboratories and Research, New York State Department of Health, New York.
Mol Microbiol. 1990 Jun;4(6):867-71. doi: 10.1111/j.1365-2958.1990.tb00659.x.
Group I introns are present in at least three bacteriophage T4 genes: td, nrdB and sunY. The transcription products of these three genes have similar intron consensus regions and secondary structures, which render them capable of guanosine-mediated in vitro autocatalytic splicing reactions. Moreover, it has been shown that the 245-amino-acid protein encoded in the td intron expresses an endonuclease that cleaves near the joining site for the two exons in the intron-deleted thymidylate synthase gene. The intron-containing td gene is resistant to the enzyme. As in the case of other group I intron-containing genes that have been described in eukaryotes, which also encode site-specific endonucleases, the td intron is highly mobile and can insert into the intron-less td gene by a process initiated by endonuclease cleavage near the insertion site. Whether intron transposition reactions have any physiological significance to the phage, or represent an early imprint on the evolution of introns, remains to be determined.
I 组内含子存在于至少三个噬菌体T4基因中：td、nrdB和sunY。这三个基因的转录产物具有相似的内含子共有区域和二级结构，这使得它们能够进行鸟苷介导的体外自催化剪接反应。此外，已经表明td内含子中编码的245个氨基酸的蛋白质表达一种内切核酸酶，该酶在缺失内含子的胸苷酸合酶基因中两个外显子的连接位点附近切割。含有内含子的td基因对该酶具有抗性。正如在真核生物中描述的其他含有I组内含子的基因的情况一样，这些基因也编码位点特异性内切核酸酶，td内含子具有高度的移动性，并且可以通过插入位点附近的内切核酸酶切割引发的过程插入到无内含子的td基因中。内含子转座反应对噬菌体是否具有任何生理意义，或者是否代表内含子进化的早期印记，仍有待确定。
