van der Vossen E A, Bol J F
Institute of Molecular Plant Sciences, Gorlaeus Laboratories, Leiden University, The Netherlands.
Virology. 1996 Jun 15;220(2):539-43. doi: 10.1006/viro.1996.0345.
The leader sequence of RNA 3 of the Leiden isolate of alfalfa mosaic virus strain 425 consists of 345 nucleotides (nt) and contains four putative stem-loop structures each with a motif in the loop that resembles the internal control region 2 (ICR2) of tRNA genes. The sequence of the 5' terminal 112 nt of this leader contains one of these stem-loop structures and is sufficient for a reduced accumulation of RNA 3 in protoplasts and a delayed accumulation in plants (E. A. G. van der Vossen et al., Nucleic Acids Res. 21, 1361-1367 (1993). A number of mutations were made in this 112-nt leader sequence to investigate its role in RNA 3 accumulation. Deletion of nucleotides 23-43, 44-90, or 55-112 and inversion or duplication of nucleotides 44-90 all abolished RNA 3 accumulation. Similarly, two base substitutions in the ICR2 motif (nucleotides 60-77) abolished RNA'3 accumulation. Mutations in the stem sections of the putative stem-loop structure had various effects on RNA 3 accumulation and supported the notion that this structure is important for plus-strand promoter activity.
苜蓿花叶病毒425株系莱顿分离株的RNA 3的前导序列由345个核苷酸（nt）组成，包含四个推定的茎环结构，每个茎环结构的环中都有一个基序，类似于tRNA基因的内部控制区2（ICR2）。该前导序列5'端112 nt的序列包含这些茎环结构之一，足以使原生质体中RNA 3的积累减少，并使植物中的积累延迟（E. A. G. van der Vossen等人，《核酸研究》21, 1361 - 1367 (1993)）。在这个112 nt的前导序列中进行了一些突变，以研究其在RNA 3积累中的作用。删除核苷酸23 - 43、44 - 90或55 - 112以及核苷酸44 - 90的倒置或重复都消除了RNA 3的积累。同样，ICR2基序（核苷酸60 - 77）中的两个碱基替换也消除了RNA 3的积累。推定的茎环结构茎部的突变对RNA 3的积累有不同影响，并支持了该结构对正链启动子活性很重要的观点。
