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Review
. 2016 Jul 2:13:118.
doi: 10.1186/s12985-016-0573-8.

Rift Valley fever virus NSs protein functions and the similarity to other bunyavirus NSs proteins

Hoai J Ly  1 , Tetsuro Ikegami  2   3   4
Affiliations
Review

Rift Valley fever virus NSs protein functions and the similarity to other bunyavirus NSs proteins

Hoai J Ly et al. Virol J. .

Abstract

Rift Valley fever is a mosquito-borne zoonotic disease that affects both ruminants and humans. The nonstructural (NS) protein, which is a major virulence factor for Rift Valley fever virus (RVFV), is encoded on the S-segment. Through the cullin 1-Skp1-Fbox E3 ligase complex, the NSs protein promotes the degradation of at least two host proteins, the TFIIH p62 and the PKR proteins. NSs protein bridges the Fbox protein with subsequent substrates, and facilitates the transfer of ubiquitin. The SAP30-YY1 complex also bridges the NSs protein with chromatin DNA, affecting cohesion and segregation of chromatin DNA as well as the activation of interferon-β promoter. The presence of NSs filaments in the nucleus induces DNA damage responses and causes cell-cycle arrest, p53 activation, and apoptosis. Despite the fact that NSs proteins have poor amino acid similarity among bunyaviruses, the strategy utilized to hijack host cells are similar. This review will provide and summarize an update of recent findings pertaining to the biological functions of the NSs protein of RVFV as well as the differences from those of other bunyaviruses.

Keywords: Bunyavirus; E3 ligase; Interferon; NSs; PKR; Phlebovirus; Rift Valley fever virus; TFIIH; Ubiquitin; p53; p62.

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Figures

Fig. 1
Fig. 1
Genetic diversity of phleboviruses. Phylogenetic analysis of available phlebovirus M-segment partial ORF (corresponding to RVFV M precursor polyprotein amino acid position 583 to 770) at amino acid level was performed. The neighbor-joining method with Kimura two-parameter distance was utilized to generate phylogenetic tree with 1000 replicates, using CLC Genomics Workbench version 7.5.2. Vectors and isolations of each virus are also shown. Relevant studies have been reported previously [, , –148]
Fig. 2
Fig. 2
Schematics of RVFV NSs-mediated TFIIH suppression. The top portion of the figure illustrates that RVFV NSs protein binds to p44, and sequesters it from the assembly site of TFIIH. Whereas the bottom portion of the figure illustrates the formation of the E3 ligase complex, consisting of cullin 1 (CUL1), Skp1, and FBXO3, and promoting the subsequent degradation of p62 through RVFV NSs
Fig. 3
Fig. 3
Schematics of RVFV NSs-mediated PKR degradation. RVFV NSs protein forms the E3 ligase complex, which consists of CUL1, Skp1, and FBXW11. The E3 ligase complex promotes the degradation of PKR via the ubiquitin-proteasome pathway. NEDD8 activating enzyme (NAE1) can be selectively inhibited by MLN4924
See this image and copyright information in PMC

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