Open AccessContributions of Two Nuclear Localization Signals of Influenza A Virus Nucleoprotein to Viral Replication
Author(s) -
Makoto Ozawa,
Ken Fujii,
Yukiko Muramoto,
S. Yamada,
Seiya Yamayoshi,
Ayato Takada,
Hideo Goto,
Taisuke Horimoto,
Yoshihiro Kawaoka
Publication year - 2007
Publication title -
journal of virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.617
H-Index - 292
eISSN - 1070-6321
pISSN - 0022-538X
DOI - 10.1128/jvi.01434-06
Subject(s) - nls , biology , nuclear localization sequence , viral replication , nuclear transport , ribonucleoprotein , nucleoprotein , virology , transcription (linguistics) , influenza a virus , orthomyxoviridae , nuclear export signal , virus , microbiology and biotechnology , cell nucleus , rna , genetics , cytoplasm , gene , linguistics , philosophy
The RNA genome of influenza A virus, which forms viral ribonucleoprotein complexes (vRNPs) with viral polymerase subunit proteins (PA, PB1, and PB2) and nucleoprotein (NP), is transcribed and replicated in the nucleus. NP, the major component of vRNPs, has at least two amino acid sequences that serve as nuclear localization signals (NLSs): an unconventional NLS (residues 3 to 13; NLS1) and a bipartite NLS (residues 198 to 216; NLS2). Although both NLSs are known to play a role in nuclear transport, their relative contributions to viral replication are poorly understood. We therefore investigated their contributions to NP subcellular/subnuclear localization, viral RNA (vRNA) transcription, and viral replication. Abolishing the unconventional NLS caused NP to localize predominantly to the cytoplasm and affected its activity in vRNA transcription. However, we were able to create a virus whose NP contained amino acid substitutions in NLS1 known to abolish its nuclear localization function, although this virus was highly attenuated. These results indicate that while the unconventional NLS is not essential for viral replication, it is necessary for efficient viral mRNA synthesis. On the other hand, the bipartite NLS, whose contribution to the nuclear transport of NP is limited, was essential for vRNA transcription and NP's nucleolar accumulation. A virus with nonfunctional NLS2 could not be generated. Thus, the bipartite NLS, but not the unconventional NLS, of NP is essential for influenza A virus replication.