PB2 polymerase subunit of Thogoto virus (Orthomyxoviridae family).

Thogoto virus (THOV) represents a new genus in the family Orthomyxoviridae. The three polymerase subunits PB1, PB2, and PA initiate transcription by a unique cap-stealing mechanism that involves the cleavage of only the m(7)GpppAm structure from cellular hnRNAs. Here, we report the cloning of the longest genomic segment of THOV coding for PB2. It comprises 2,375 nucleotides encoding a single large open reading frame flanked by the conserved terminal regions typical for orthomyxoviruses. The deduced amino acid sequence corresponds to a protein of 769 amino acids, with an estimated Mr of 88,042. Expression of the PB2 cDNA in mammalian cells revealed nuclear accumulation of the recombinant protein, consistent with the replication of THOV in the cell nucleus.