Bonocora Richard P, Shub David A
Department of Biological Sciences, State University of New York at Albany, Albany, NY 12222, USA.
J Bacteriol. 2004 Dec;186(23):8153-5. doi: 10.1128/JB.186.23.8153-8155.2004.
Group I introns are inserted into genes of a wide variety of bacteriophages of gram-positive bacteria. However, among the phages of enteric and other gram-negative proteobacteria, introns have been encountered only in phage T4 and several of its close relatives. Here we report the insertion of a self-splicing group I intron in the coding sequence of the DNA polymerase genes of PhiI and W31, phages that are closely related to T7. The introns belong to subgroup IA2 and both contain an open reading frame, inserted into structural element P6a, encoding a protein belonging to the HNH family of homing endonucleases. The introns splice efficiently in vivo and self-splice in vitro under mild conditions of ionic strength and temperature. We conclude that there is no barrier for maintenance of group I introns in phages of proteobacteria.
I类内含子插入到多种革兰氏阳性菌噬菌体的基因中。然而，在肠道菌和其他革兰氏阴性变形菌的噬菌体中，仅在噬菌体T4及其几个近亲中发现了内含子。在此，我们报道了一个自我剪接的I类内含子插入到PhiI和W31的DNA聚合酶基因编码序列中，PhiI和W31是与T7密切相关的噬菌体。这些内含子属于IA2亚组，并且都包含一个开放阅读框，插入到结构元件P6a中，编码一种属于归巢内切核酸酶HNH家族的蛋白质。这些内含子在体内能有效剪接，在温和的离子强度和温度条件下能在体外自我剪接。我们得出结论，对于变形菌噬菌体中I类内含子的维持不存在障碍。
