Multiple leader RNAs and messenger RNAs are transcribed from the La Crosse virus small genome segment

Nucleotide sequencing has demonstrated that the Small genome segment of Bunyaviruses contains the genetic information for two viral proteins (N and NSs) in overlapping reading frames (Akashi and Bishop, 1983; Cabradilla et al., in press). Using 3' end-labeled genome probes, La Crosse virus (LAC) infected cells were shown to contain three leader RNAs, which start at position 1 and terminate at approximate positions 74, 95, and 115 from the 3' end of the genome. Primer extension and S1 mapping studies have shown that LAC-infected cells contain seven mRNAs, five of which initiate at positions 1, 74, 101, 117, and 123 and two more which initiate at approximate positions 147 and 159 from the 3' end of the Small genome segment. The existence of multiple leader RNAs and mRNAs from the Small genome segment may allow access to both overlapping reading frames by ribosomes that still initiate only at 5' proximal AUGs, without the need to splice the mRNA.