Abstract
SUMOylation is a reversible covalent process between a small ubiquitin-like modifier (SUMO) and its target protein and has become a crucial regulator of protein functions. Here, we report that Bombyx mori nucleopolyhedrovirus (BmNPV) may take advantage of the host SUMOylation system to enhance its own replication, similar to many other viruses. Both the knockdown of BmSUMO by RNAi and chemical blocking by ginkgolic acid both impaired BmNPV replication. Using site mutation and pull-down assays, we found that lysine K70 of the protein kinase-interacting protein (PKIP), which is conserved in all Alphabaculoviruses, was modified by SUMO. Mutation of K70 in PKIP led to its translocation from the cytoplasm to the nucleus. Knockout and rescue experiments showed that the rescue of PKIP mutant virus with wild-type PKIP restored BmNPV replication to the normal level, but this was not true for the K70R mutation. Altogether, these results show that SUMOylation of PKIP plays a key role in BmNPV replication.
Highlights
Post-translational protein modifications (PTMs), such as ubiquitinoylation, phosphorylation, neddylation, and glycosylation, enable cells to control the function of proteins.A small ubiquitin-like modifier (SUMO) was characterized during a study on the effect of covalent modifications on the nuclear import of RanGAP1 [1,2]
The cDNA sequence and amino acid sequence of BmSUMO were aligned against the silkworm genomic sequence using NCBI BLAST
We found that some proteins from Bombyx mori nucleopolyhedrovirus (BmNPV) may be modified by SUMO, such as protein kinase-interacting protein (PKIP), which is an essential protein related to budded virus (BV) production [33,34]
Summary
Post-translational protein modifications (PTMs), such as ubiquitinoylation, phosphorylation, neddylation, and glycosylation, enable cells to control the function of proteins.A small ubiquitin-like modifier (SUMO) was characterized during a study on the effect of covalent modifications on the nuclear import of RanGAP1 [1,2]. SUMO interacts with the substrate proteins in two ways. One way is by covalently attaching SUMO to the ε-amino group of lysine residues of the substrate protein to regulate several biological processes, such as transcription regulation, cell cycle process, innate immunity modulation, and DNA damage repair [3,4,5]. Binding to the substrate protein involves at least four enzymes, including an E1-activating enzyme complex (SAE1/SAE2), a unique. E2-conjugating enzyme (Ubc9), and some E3 ligases (such as PIAS), which are conjugated to its substrates through the lysine (K) at the consensus motif (ψKxE), where ψ is a hydrophobic amino acid [6,7,8]. The non-covalent interaction of SUMO and its substrate occurs through SUMO-interacting motifs, which affect its activity by non-covalent attachment
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