Identification of amino acids in Marburg virus VP40 that are important for virus-like particle budding

The matrix protein VP40 of Marburg virus promotes the formation and release of virus-like particles (VLPs). Marburg virus VP40 interacts with cellular Tsg101 via its L domain motif; however, mutation of this motif does not affect VLP budding or the accumulation of VP40 in multivesicular bodies (MVBs), which are platforms for virus particle formation. To identify regions of Marburg virus VP40 that are important for VLP budding, we examined deletion mutants and alanine-scanning mutants at the N- and C-terminus of VP40 for their involvement in VLP budding. VLPs were not detected in the presence of alanine-replacement mutants at Ile39 and Thr40, and the level of VLP budding for the alanine mutant at Asn297 was decreased. Moreover, these mutants did not accumulate in MVBs. Our results suggest the involvement of a novel host factor(s) in VLP budding and VP40 transport to MVBs.