Proliferating cell nuclear antigen transcription is repressed through an E2F consensus element and activated by geminivirus infection in mature leaves
Proliferating cell nuclear antigen transcription is repressed through an E2F consensus element and activated by geminivirus infection in mature leaves
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DOI：
10.1105/tpc.13.6.1437
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发表时间：
2001-06-01
期刊：
影响因子：
11.6
通讯作者：
Hanley-Bowdoin, L
中科院分区：
文献类型：
--
作者：
Egelkrout, EM;Robertson, D;Hanley-Bowdoin, L
双生病毒属番茄金色花叶病毒（TGMV）在缺乏可检测水平的DNA复制酶的分化的植物细胞中扩增其DNA基因组。早期的研究表明，TGMV诱导增殖细胞核抗原（PCNA）的积累，DNA聚合酶6的持续性因子，在本氏烟草成熟细胞。我们试图确定PCNA蛋白的积累是否反映了宿主基因的转录激活。RNA凝胶印迹分析在幼叶中检测到一个类似于1200个核苷酸的PCNA转录本。同样的RNA在受感染但不健康的植物的成熟叶片中被发现。报告基因分析表明，一个633 bp的启动子片段的N。本塞姆那PCNA基因支持在培养细胞和健康转基因植物的幼叶但不成熟叶中的高水平表达。与此相反，PCNA启动子活性检测在年轻和成熟叶片的TGMV感染的植物。发育研究建立了症状严重程度，病毒DNA积累，PCNA启动子活性和内源性PCNA mRNA水平之间的密切关系。PCNA启动子中的E2F共有元件的突变对其在幼叶中的活性没有影响，但在健康的成熟叶中增加了转录。与野生型PCNA启动子不同，TGMV感染对突变型E2F启动子的活性没有可检测的影响。总之，这些结果表明，双生病毒感染诱导宿主复制因子的积累，通过激活其基因在成熟组织中的转录，最有可能通过克服E2F介导的抑制。
The geminivirus tomato golden mosaic virus (TGMV) amplifies its DNA genome in differentiated plant cells that lack detectable levels of DNA replication enzymes. Earlier studies showed that TGMV induces the accumulation of proliferating cell nuclear antigen (PCNA), the processivity factor for DNA polymerase 6, in mature cells of Nicotiana benthamiana. We sought to determine if PCNA protein accumulation reflects transcriptional activation of the host gene. RNA gel blot analysis detected an similar to 1200-nucleotide PCNA transcript in young leaves. The same RNA was found in mature leaves of infected but not healthy plants. Reporter gene analysis showed that a 633-bp promoter fragment of the N. benthamiana PCNA gene supports high levels of expression in cultured cells and in young but not mature leaves of healthy transgenic plants. In contrast, PCNA promoter activity was detected in both young and mature leaves of TGMV-infected plants. Developmental studies established a strong relationship between symptom severity, viral DNA accumulation, PCNA promoter activity, and endogenous PCNA mRNA levels. Mutation of an E2F consensus element in the PCNA promoter had no effect on its activity in young leaves but increased transcription in healthy mature leaves. Unlike the wild-type PCNA promoter, TGMV infection had no detectable effect on the activity of the mutant E2F promoter. Together, these results demonstrate that geminivirus infection induces the accumulation of a host replication factor by activating transcription of its gene in mature tissues, most likely by overcoming E2F-mediated repression.