Lin Xu'ai, Chen Yin, Yi Yongzhu, Yan Jie, Zhang Zhifang
Department of Medical Microbiology and Parasitology, School of Medicine, Zhejiang University, Hangzhou 310058, PR China.
J Microbiol. 2008 Aug;46(4):429-35. doi: 10.1007/s12275-007-0163-y. Epub 2008 Aug 31.
The aim of this study was to analyze the characteristics of Bombyx mori nucleopolyhedrovirus (BmNPV) ubiquitin gene promoter and the effects of conserved motifs, such as TAAG, TATA, and CAAT, along with baculovirus enhancer homologous region 3 (hr3), on promoter activity. Ubiquitin gene of BmNPV was expressed during the late phase of virus infection. In the presence of viral factors, significant reduction of promoter activity was observed by deletion of -382 to -124 bp upstream of ATG. The fragment between -187 and -383 bp upstream of ATG, including distal TAAG, CAAT motif, and TATA box, could also drive expression of the reporter gene. The mutation of cis-elements TATA boxes and TAAG motifs significantly decreased the promoter's activity, while CAAT mutations enhanced promoter activity by 2-or 3-fold, as compared with the native promoter. In the presence of BmNPV, hr3, both located downstream of the reporter gene of the same vector, and separate vector, could significantly enhance transcription activity of ubiquitin promoter as compared to the control. We concluded that BmNPV ubiquitin gene might be regulated by dual sets of promoter elements, where TAAG and TATA box may positively regulate the expression of ubiquitin, while CAAT motif functions as a negative regulator. Viral factor(s) play an important role in the co-activation of hr3 and promoter.
本研究旨在分析家蚕核型多角体病毒(BmNPV)泛素基因启动子的特征,以及保守基序(如TAAG、TATA和CAAT)连同杆状病毒增强子同源区域3(hr3)对启动子活性的影响。BmNPV的泛素基因在病毒感染后期表达。在病毒因子存在的情况下,通过缺失ATG上游-382至-124 bp区域,观察到启动子活性显著降低。ATG上游-187至-383 bp之间的片段,包括远端TAAG、CAAT基序和TATA框,也可驱动报告基因的表达。顺式元件TATA框和TAAG基序的突变显著降低了启动子的活性,而CAAT突变与天然启动子相比,使启动子活性提高了2至3倍。在BmNPV存在的情况下,与对照相比,位于同一载体报告基因下游的hr3以及单独的载体均可显著增强泛素启动子的转录活性。我们得出结论,BmNPV泛素基因可能受两组启动子元件调控,其中TAAG和TATA框可能正向调控泛素的表达,而CAAT基序起负调控作用。病毒因子在hr3与启动子的共激活中起重要作用。