Nucleotide sequence of the genome and complete amino acid sequence of the polyprotein of tick-borne encephalitis virus

Abstract

The sequence of the genome of tick-borne encephalitis (TBE) virus (Far Eastern subtype, strain Sofjin) coding for structural proteins and nonstructural protein NS1 has been previously reported ( A. G. Pletnev, V. F. Yamshchikov, and V. M. Blinov, 1986, FEBS Lett. 200, 317–321; Yamshchikov and Pletnev, 1988, Nucleic Acids Res. 16, 7750 . Now we have cloned and sequenced the genomic RNA that encodes all nonstructural proteins. Together with our earlier sequence analyses, these data show that the TBE genome is 10,477 bases in length with a single open reading frame extending from nucleotides 127 to 10,363, encoding 3412 amino acids. The 5′- and 3′-noncoding regions have stem-loop structures. The polyprotein precursor is proteolytically cleaved, apparently by a mechanism resembling that proposed for the expression of polyproteins of the other flaviviruses, such as yellow fever and Kunjin viruses. The deduced TBE gene order is 5′-C-pre(M)M-E-NS1-NS2A-NS2B-NS3-ns4a-NS4B-NS5-3′. The genome structure and the polyprotein of TBE virus is similar to mosquito-borne flaviviruses, although TBE virus is transmitted by ticks. Comparison of the sequence homology of polyproteins of flaviviruses suggests that TBE virus is more closely related to yellow fever virus than to other serological subgroups of flaviviruses. The hydrophobicity profile of the TBE polyprotein is similar to those of other flaviviruses. Nonstructural proteins NS2A, NS2B, ns4a, and NS4B are extremely hydrophobic, suggesting that these proteins are likely associated with cellular membranes. Proteins E, NS1, NS3, and NS5 are the most conserved and these proteins may be involved in the general activities related to viral reproduction.