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The nucleoprotein of Marburg virus is phosphorylated
S Becker1, S Huppertz, H D Klenk
1Institut für Virologie, Marburg, Germany.
Abstract:
The nucleoprotein (NP) of Marburg virus (MBG), a filovirus, is encoded by the gene closest to the 3' end of the non-segmented negative-strand RNA genome. Sequence comparison has indicated that NP is the functional equivalent to the nucleoproteins of paramyxoviruses and rhabdoviruses. Expression of recombinant NP in two eukaryotic systems using vaccinia virus and baculovirus (vectors pSC11 and pAcYMB1, respectively) and analysis of MBG-specific proteins have demonstrated that the NP of MBG is phosphorylated. The NP appeared in two forms differing in M(r) by about 2K (94K and 92K respectively). Dephosphorylation clearly demonstrated that the 94K form is phosphorylated whereas the 92K form is unphosphorylated. In virion particles NP was exclusively present in the phosphorylated form. These findings suggest that only the phosphorylated NP can form nucleocapsid complexes and interact with the genomic RNA.
Insights
Marburg virus nucleoprotein (NP) is phosphorylated, existing in two forms. Only the phosphorylated form of this filovirus protein is found in virions, suggesting it
Area of Science:
- Virology
- Molecular Biology
- Protein Biochemistry
Background:
- Marburg virus (MBG), a filovirus, possesses a non-segmented negative-strand RNA genome.
- The nucleoprotein (NP) gene is located closest to the 3' end of the MBG genome.
- Sequence comparisons suggest MBG NP is functionally analogous to nucleoproteins in paramyxoviruses and rhabdoviruses.
Purpose of the Study:
- To investigate the phosphorylation status of Marburg virus nucleoprotein (NP).
- To determine the functional implications of NP phosphorylation in Marburg virus.
Main Methods:
- Expression of recombinant MBG NP in eukaryotic systems (vaccinia virus and baculovirus vectors).
- Analysis of MBG-specific proteins, including phosphorylation and dephosphorylation studies.
- Examination of NP form within purified Marburg virus virions.
Main Results:
- MBG NP is phosphorylated and exists in two forms: a 94K phosphorylated form and a 92K unphosphorylated form.
- Dephosphorylation experiments confirmed the differential phosphorylation states of the two NP forms.
- Within Marburg virus virions, NP was exclusively detected in its phosphorylated (94K) form.
Conclusions:
- Phosphorylation is a critical modification for Marburg virus nucleoprotein (NP).
- Only phosphorylated NP appears to be incorporated into virions and capable of forming nucleocapsid complexes with genomic RNA.
- This suggests a regulatory role for NP phosphorylation in Marburg virus replication and assembly.