The C-terminal helical domain of dengue virus precursor membrane protein is involved in virus assembly and entry

The role of the α-helical domain (MH) of dengue virus (DENV) precursor membrane protein in replication was investigated by site-directed mutagenesis. Proline substitutions of three residues (120, 123 and 127) at the C-terminus, but not those at the N-terminus of MH domain, reduced the virus-like particles of DENV1, DENV2 and DENV4 detected in supernatants. In a DENV2 replicon trans-packaging system, these three mutations suppressed particles detected; two of them (I123P and V127P) also affected viral entry. In the context of DENV2 genome-length RNA, all three mutations reduced virion assembly and virus spreading in cell culture. Analysis of revertants showed that mutation A120P could partially support viral infection cycle; in contrast, mutations I123P and V127P were lethal, and adaptations of I123P → I123L and V127P → V127L were required to restore the viral infection cycle. These findings demonstrate that the C-terminus of the MH domain is involved in both assembly and entry of DENV.