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