Functional genomics of chilo iridescent virus: a transcriptoproteomic approach

Iridoviruses are disease causing agents in (pest) insects, fishes and amphibians with serious ecological and economic impacts. Insight in the composition of the virions and the transcriptional regulation of the virion protein genes is crucial to unravel the biology of this lesser known family of viruses. In this thesis, the virions of Chilo iridescent virus (CIV) (genus Iridovirus) were analyzed by mass spectrometry, revealing 54 virion proteins. A novel transcriptomic approach for non-polyadenylated RNA transcripts, called LACE, was developed and applied to unravel the temporal class of the virion protein genes. This showed that many virion protein genes were expressed as early genes. Another intriguing finding is that an infected cell-specific 100 kDa protein interacted with a crucial delayed-early promoter motif in the DNA polymerase gene and it turned out that this motif was conserved in other (putative) delayed early genes in CIV and other iridoviruses. The hypothesis is that this 100 kDa protein is responsible for transcriptional activation of delayed-early genes. CIV is an example of an invertebrate iridoviruses that deals with induction and inhibition of apoptosis during infection. In this study, a gene for a functional inhibitor of apoptosis (193R), unique for an iridovirus, was identified. In addition, several candidates for pro-apoptotic proteins were found in the virion. In this dissertation fundamental knowledge was obtained on the proteome of CIV virions and the regulation of CIV gene expression. Due to the development and application of novel technics, this thesis provides new venues to answer remaining questions concerning the infection cycle of this interesting iridovirus. Keywords Iridovirus, transcriptomics, proteomics, virus-host interaction