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Complex nuclear localization signals in the matrix protein of vesicular stomatitis virus
Doreen R Glodowski1, Jeannine M Petersen, James E Dahlberg
1Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706-1532, USA.
Abstract:
The matrix (M) protein of vesicular stomatitis virus (VSV) functions from within the nucleus to inhibit bi-directional nucleocytoplasmic transport. Here, we show that M protein can be imported into the nucleus by an active transport mechanism, even though it is small enough (approximately 27 kDa) to diffuse through nuclear pore complexes. We map two distinct nuclear localization signal (NLS)-containing regions of M protein, each of which is capable of directing the nuclear localization of a heterologous protein. One of these regions, comprising amino acids 47-229, is also sufficient to inhibit nucleocytoplasmic transport. Two amino acids that are conserved among the matrix proteins of vesiculoviruses are important for nuclear localization, but are not essential for the inhibitory activity of M protein. Thus, different regions of M protein function for nuclear localization and for inhibitory activity.
Insights
Vesicular stomatitis virus matrix protein actively enters the nucleus and inhibits transport. Distinct regions of the M protein mediate nuclear import and transport inhibition.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Vesicular stomatitis virus (VSV) matrix (M) protein is known to inhibit nucleocytoplasmic transport from the nucleus.
- The mechanism of M protein's nuclear localization and its precise role in transport inhibition require further elucidation.
Purpose of the Study:
- To investigate the mechanism of VSV M protein's nuclear import.
- To identify the specific regions of M protein responsible for nuclear localization and nucleocytoplasmic transport inhibition.
Main Methods:
- Nuclear localization signal (NLS) mapping using heterologous protein import assays.
- Site-directed mutagenesis to identify key amino acids involved in nuclear import and inhibition.
Main Results:
- VSV M protein utilizes an active transport mechanism for nuclear import, despite its small size.
- Two distinct NLS-containing regions within M protein were identified, both capable of directing nuclear localization.
- A specific region (amino acids 47-229) was found to be sufficient for inhibiting nucleocytoplasmic transport.
- Conserved amino acids are important for nuclear localization but not essential for inhibitory activity.
Conclusions:
- VSV M protein employs distinct functional domains for nuclear import and for the inhibition of nucleocytoplasmic transport.
- Understanding these distinct functions provides insights into viral pathogenesis and nuclear transport regulation.