Gimble F S
Center for Genome Research, Institute of Biosciences and Technology, The Texas A and M University System Health Science Center, 2121 W. Holcombe Blvd., Texas A and M University, Houston, TX, USA.
FEMS Microbiol Lett. 2000 Apr 15;185(2):99-107. doi: 10.1111/j.1574-6968.2000.tb09046.x.
Persistence of a mobile DNA element in a population reflects a balance between the ability of the host to eliminate the element and the ability of the element to survive and to disseminate to other individuals. In each of the three biological kingdoms, several families of a mobile DNA element have been identified which encode a single protein that acts on nucleic acids. Collectively termed homing endonuclease genes (HEGs), these elements employ varied strategies to ensure their survival. Some members of the HEG families have a minimal impact on host fitness because they associate with genes having self-splicing introns or inteins that remove the HEGs at the RNA or protein level. The HEG and the intron/intein gene spread throughout the population by a gene conversion process initiated by the HEG-encoded endonuclease called 'homing' in which the HEG and intron/intein genes are copied to cognate alleles that lack them. The endonuclease activity also contributes to a high frequency of lateral transmission of HEGs between species as has been documented in plants and other systems. Other HEGs have positive selection value because the proteins have evolved activities that benefit their host organisms. The success of HEGs in colonizing diverse genetic niches results from the flexibility of the encoded endonucleases in adopting new specificities.
可移动DNA元件在种群中的持续存在反映了宿主消除该元件的能力与该元件存活并传播到其他个体的能力之间的平衡。在三个生物界的每一个中，都已鉴定出几个可移动DNA元件家族，它们编码一种作用于核酸的单一蛋白质。这些元件统称为归巢内切核酸酶基因（HEGs），它们采用多种策略来确保自身的存活。HEG家族的一些成员对宿主适应性的影响最小，因为它们与具有自我剪接内含子或蛋白质内含子的基因相关联，这些内含子在RNA或蛋白质水平上去除HEGs。HEG和内含子/蛋白质内含子基因通过由HEG编码的内切核酸酶引发的基因转换过程在种群中传播，这种过程称为“归巢”，其中HEG和内含子/蛋白质内含子基因被复制到缺乏它们的同源等位基因中。如在植物和其他系统中所记录的那样，内切核酸酶活性也有助于HEGs在物种间的高频横向传播。其他HEGs具有正选择价值，因为这些蛋白质已经进化出有利于其宿主生物体的活性。HEGs在定殖于不同遗传生态位方面的成功源于编码内切核酸酶在采用新特异性方面的灵活性。
