Suárez-López P, Martínez-Salas E, Hernández P, Gutiérrez C
Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma, Cantoblanco, Madrid, Spain.
Virology. 1995 Apr 1;208(1):303-11. doi: 10.1006/viro.1995.1153.
Wheat dwarf virus (WDV) is a member of the geminivirus group, unique plant DNA viruses which replicate exclusively via dsDNA replication intermediates. The large intergenic region (LIR), a nontranscribed regulatory region, contains an inverted repeat with the potential to form a stem-loop structure in which the initiation site for WDV (+)strand (virion-sense) DNA replication has been mapped. In this work, we have studied by two-dimensional electrophoresis and by electron microscopy the DNA structure of the WDV LIR and we have identified a DNA sequence which confers a static DNA curvature. This is the first report of the occurrence of DNA bending in the regulatory region of a geminivirus genome. The bending locus, defined by an 80-bp cluster of A(T) tracts, is located downstream from the potential stem-loop. The A(T) tract proximal to the stem-loop structure is separated by 14 bp from the inverted repeat, and deletion of distal A(T) tracts abolished the curvature of the new WDV deltaLIR. The bending center maps approximately 80 bp downstream from the putative initiation site for (+)strand DNA replication and approximately 70 bp upstream from the TATA box for virion-sense transcription. The possible implications of the DNA bending locus as a regulatory element of WDV DNA replication and/or virion-sense transcription are discussed.
小麦矮缩病毒（WDV）是双生病毒组的成员，是一类独特的植物DNA病毒，仅通过双链DNA复制中间体进行复制。大基因间隔区（LIR）是一个非转录调控区，包含一个反向重复序列，有可能形成茎环结构，WDV（+）链（病毒链）DNA复制的起始位点已定位在该结构中。在这项工作中，我们通过二维电泳和电子显微镜研究了WDV LIR的DNA结构，并鉴定出一个赋予静态DNA曲率的DNA序列。这是双生病毒基因组调控区出现DNA弯曲的首次报道。由80个碱基对的A（T）序列簇定义的弯曲位点位于潜在茎环的下游。茎环结构附近的A（T）序列与反向重复序列相隔14个碱基对，删除远端A（T）序列消除了新的WDV deltaLIR的曲率。弯曲中心位于（+）链DNA复制假定起始位点下游约80个碱基对处，以及病毒链转录TATA框上游约70个碱基对处。讨论了DNA弯曲位点作为WDV DNA复制和/或病毒链转录调控元件的可能意义。
