Wank H, SanFilippo J, Singh R N, Matsuura M, Lambowitz A M
Department of Chemistry and Biochemistry, University of Texas at Austin 78712, USA.
Mol Cell. 1999 Aug;4(2):239-50. doi: 10.1016/s1097-2765(00)80371-8.
Group II introns encode reverse transcriptases that promote RNA splicing (maturase activity) and then with the excised intron form a DNA endonuclease that mediates intron mobility by target DNA-primed reverse transcription (TPRT). Here, we show that the primary binding site for the maturase (LtrA) encoded by the Lactococcus lactis Ll.LtrB intron is within a region of intron domain IV that includes the start codon of the LtrA ORF. This binding is enhanced by other elements, particularly domain I and the EBS/IBS interactions, and helps position LtrA to initiate cDNA synthesis in the 3' exon as occurs during TPRT. Our results suggest how the maturase functions in RNA splicing and support the hypothesis that the reverse transcriptase coding region was derived from an independent genetic element that was inserted into a preexisting group II intron.
II类内含子编码逆转录酶，该酶促进RNA剪接（成熟酶活性），然后与切除的内含子一起形成一种DNA内切核酸酶，通过靶DNA引发的逆转录（TPRT）介导内含子移动。在此，我们表明，乳酸乳球菌Ll.LtrB内含子编码的成熟酶（LtrA）的主要结合位点位于内含子结构域IV的一个区域内，该区域包括LtrA开放阅读框的起始密码子。这种结合会被其他元件增强，特别是结构域I和EBS/IBS相互作用，并且有助于定位LtrA，以便在TPRT过程中在3'外显子中启动cDNA合成。我们的结果表明了成熟酶在RNA剪接中的作用方式，并支持以下假设：逆转录酶编码区源自一个插入到先前存在的II类内含子中的独立遗传元件。
