| Abstract: | We have cloned and sequenced RNA encoding all virion and nonstructural proteins of tick-borne encephalitis virus (TBEV). Its length is 10,477 bases with a single open reading frame (nucleotides 127-10,363) encoding 3412 amino acids. The 5'- and 3'-noncoding regions have stem- and- loop structure. The polyprotein precursor is proteolytically cleaved, apparently, by a mechanism resembling that proposed for the expression of polyproteins of other flaviviruses, such as yellow fever, West Nile and Kunjin viruses. The deduced TBEV gene order is 5'-C-preM (M)-E-NS1-NS2A-NS2B-NS3-NS4A-NS4B-NS5++ +-3'. The genome and the polyprotein of TBEV and other flaviviruses appears to be structurally similar, although these flaviviruses are transmitted to and from their vertebrate hosts by different carriers, such as ticks or mosquitoes. Analysis of sequence homologies of polyproteins of flaviviruses suggests that TBEV is more closely related to yellow fever virus than to other serological subgroups of flaviviruses (West Nile or Dengue viruses). The hydrophobic profiles of the flaviviruses are highly conservative. Nonstructural proteins NS2A, NS2B, NS4A and NS4B are extremely hydrophobic, suggesting that they are likely to be associated with cellular membranes. Proteins E, NS1, NS3 and NS5 are the most conservative and may be involved in general enzymatic activities related to viral replication and virion assembly. |
