Characterization of nucleotides 28-43 of the human parainfluenza virus type 3 antigenomic promoter in genome replication

Human parainfluenza virus type 3 (HPIV3) is a significant cause of lower respiratory tract infections in infants and young children worldwide. During replication of HPIV3, the 96-nucleotide antigenomic promoter directs synthesis of genomic RNA. Previous work showed that nucleotides 1-12 (from the terminus) were critical in promoting replication of an HPIV3 minireplicon, but the role of nucleotides 13-96 was not investigated. However, the 13-96 region of the genomic promoter was recently characterized and found to have elements involved in promoting replication. Therefore, to clarify the role of antigenomic promoter nucleotides 13-96 in replication, a series of mutations were introduced that collectively scanned this region in an HPIV3 minireplicon. Notably, mutation of nucleotides 13-39 significantly deceased replication, suggesting that this region regulates replication. Further analysis of the 13-39 element revealed a complicated control element with both stimulatory and repressing elements. Specifically, nucleotide 28 (and possibly 21-27) was shown to repress RNA replication, while flanking sequences had a stimulatory effect. The precise role of the 13-39 region is not known, but the differences between this region of the antigenomic promoter and an analogous region of the genomic promoter may contribute to the increased activity of the antigenomic promoter in directing genome replication