| Summary: | 博士 === 國立臺灣大學 === 動物學研究研究所 === 95 === This study investigates white spot syndrome virus (WSSV) gene expression levels in the cells of two hosts (Penaeus monodon and Litopenaeus vannamei). Microarray and EST analysis of the mRNA profiles in WSSV-infected P. monodon cells were used to identify WSSV genes that were very highly expressed. Results showed that the mRNA of the WSSV icp11 gene consistently had the highest copy number of all other viral transcripts (eg. 3x higher than the transcripts of the major envelope protein, VP28). At the protein level in WSSV-infected L. vannamei, 2-DE gel analysis and MS/MS protein identification also showed that this WSSV non-structural protein has the highest expression levels so far reported in WSSV-infected cells. However, this novel protein has no sequence homology to any other known protein, and its function remains unknown. Therefore, by using structural and functional analysis, we successfully characterized its multiple biological roles. ICP11 is capable of homo-oligomerization and localizing in both the cytoplasm and nucleus of the host cell and transfected insect cell. A Far-Western blot confirmed ICP11 can interact with the histone protein. We also found that ICP11 exhibits Mg2+ dependent nuclease activity. Additional competitive binding assays further suggested that in the presence of Mg2+ and sufficient ICP11, both of these functions are fulfilled. We therefore hypothesize that ICP11 competes with host DNA to bind to histone protein, and when all of the eligible DNA binding sites are filled, any excess ICP11 will remain unbound and act as a DNase to digest host DNA. These functions could easily result in nucleosome disorder and lead to cell death.
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