Multiple vesiculoviral matrix proteins inhibit both nuclear export and import

The matrix (M) protein of vesicular stomatitis virus inhibits both nuclear import and export. Here, we demonstrate that this inhibitory property is co nserved between the M proteins from two other vesiculoviruses, chandipura v irus and spring viremia carp virus. All three M proteins completely block n uclear transport of spliced mRNA, small nuclear RNAs, and small nuclear rib onucleoproteins and slow the nuclear transport of many other cargoes. In al l cases where transport was merely slowed by the M proteins, the chandipura virus M protein had the strongest inhibitory activity. When expressed in t ransfected HeLa cells, active M proteins displayed prominent association wi th the nuclear rim. Moreover, mutation of a conserved methionine abolished both the inhibitory activity and efficient targeting of the M proteins to t he nuclear rim. We propose that all of the vesiculoviral M proteins associa te with the same nuclear target, which is likely to be a component of the n uclear pore complex.