Nuclear and mitochondrial localization signals overlap within bovine herpesvirus 1 tegument protein VP22.
VP22, a tegument protein of bovine herpesvirus 1, accumulates in the nucleus of infected and transiently transfected cells. Previous studies indicated a possible regulatory function of VP22 within nuclei, but how VP22 enters nuclei is unknown. Despite the abundance of basic residues within this protein, no classic nuclear localization signal (NLS) motif has been identified. To identify the signal directing nuclear accumulation, a series of truncations, internal deletions, and point mutations were constructed. Fluorescence microscopy of cells transfected with VP22 constructs indicated that a sequence of 103 residues is necessary and sufficient for nuclear localization. This NLS sequence is conformation-sensitive in contrast to a classical sequential NLS. Energy depletion assays and co-immunoprecipitation suggested that this NLS sequence also binds histone H4, resulting in nuclear retention of VP22. In addition, a mitochondrial targeting sequence was identified at the C-terminal 49 amino acids, which overlapped the sequence required for nuclear targeting. Our findings demonstrate the diversity of VP22 protein to localize within the cell and provide the opportunity for VP22 to direct cargo specifically to different subcellular compartments.
Zhu
Jun
J
Department of Animal Health, University of Wisconsin, Madison, Wisconsin 53706, USA.
Qiu
Zhaohua
Z
Wiese
Christiane
C
Ishii
Yohei
Y
Friedrichsen
Jen
J
Rajashekara
Gireesh
G
Splitter
Gary A
GA
D000818:Animals; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism*; D017930:Genes, Reporter; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015678:Viral Structural Proteins / Q000235:genetics* / Q000378:metabolism
D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D015678:Viral Structural Proteins; C434023:tegument protein VP22, bovine herpesvirus 1