Unusual transcripts in La Crosse virus-infected cells and the site for nucleocapsid assembly.

The La Crosse virus S genome segment is known to code for two plus-strand transcripts, free S-mRNA (nucleotide [nt] -15 to 886) and encapsidated antigenome RNA (nt 1 to 983). Early in infection only these plus-strand transcripts could be detected, but at later times plus-strand RNAs representing nt 1 to 886 in an encapsidated form and nt -15 to 983 as a free RNA could also be seen, as well as S-mRNA in an encapsidated form. The encapsidated S-mRNA became relatively important at later times because the free S-mRNA turned over rapidly after 5 h postinfection. The existence of these unusual RNAs and their presence as either free or encapsidated species suggests that the site for nucleocapsid assembly is located at the 5' ends of the genome and antigenome chains.