Martínez-Rodríguez Laura, García-Rodríguez Fernando M, Molina-Sánchez María Dolores, Toro Nicolás, Martínez-Abarca Francisco
a Grupo de Ecología Genética; Estación Experimental del Zaidín; Consejo Superior de Investigaciones Científicas ; Granada , Spain.
RNA Biol. 2014;11(8):1061-71. doi: 10.4161/rna.32092. Epub 2014 Oct 31.
Group II introns are self-splicing RNAs and site-specific mobile retroelements found in bacterial and organellar genomes. The group II intron RmInt1 is present at high copy number in Sinorhizobium meliloti species, and has a multifunctional intron-encoded protein (IEP) with reverse transcriptase/maturase activities, but lacking the DNA-binding and endonuclease domains. We characterized two RmInt1-related group II introns RmInt2 from S. meliloti strain GR4 and Sr.md.I1 from S. medicae strain WSM419 in terms of splicing and mobility activities. We used both wild-type and engineered intron-donor constructs based on ribozyme ΔORF-coding sequence derivatives, and we determined the DNA target requirements for RmInt2, the element most distantly related to RmInt1. The excision and mobility patterns of intron-donor constructs expressing different combinations of IEP and intron RNA provided experimental evidence for the co-operation of IEPs and intron RNAs from related elements in intron splicing and, in some cases, in intron homing. We were also able to identify the DNA target regions recognized by these IEPs lacking the DNA endonuclease domain. Our results provide new insight into the versatility of related group II introns and the possible co-operation between these elements to facilitate the colonization of bacterial genomes.
II类内含子是在细菌和细胞器基因组中发现的自我剪接RNA和位点特异性移动反转录元件。II类内含子RmInt1在苜蓿中华根瘤菌物种中以高拷贝数存在，并且具有带有逆转录酶/成熟酶活性的多功能内含子编码蛋白（IEP），但缺乏DNA结合和内切核酸酶结构域。我们从苜蓿中华根瘤菌菌株GR4中鉴定了两个与RmInt1相关的II类内含子RmInt2，以及从百脉根菌株WSM419中鉴定了Sr.md.I1，并对它们的剪接和移动活性进行了表征。我们使用了基于核酶ΔORF编码序列衍生物的野生型和工程化内含子供体构建体，并确定了与RmInt1关系最疏远的元件RmInt2的DNA靶标要求。表达IEP和内含子RNA不同组合的内含子供体构建体的切除和移动模式为相关元件的IEP和内含子RNA在内含子剪接以及某些情况下在内含子归巢中的合作提供了实验证据。我们还能够鉴定出这些缺乏DNA内切核酸酶结构域的IEP所识别的DNA靶标区域。我们的结果为相关II类内含子的多功能性以及这些元件之间可能的合作以促进细菌基因组的定殖提供了新的见解。
