SARS coronavirus protein 7a interacts with human Ap4A-hydrolase

Abstract

The SARS coronavirus (SARS-CoV) open reading frame 7a (ORF 7a) encodes a 122 amino acid accessory protein. It has no significant sequence homology with any other known proteins. The 7a protein is present in the virus particle and has been shown to interact with several host proteins; thereby implicating it as being involved in several pathogenic processes including apoptosis, inhibition of cellular protein synthesis, and activation of p38 mitogen activated protein kinase. In this study we present data demonstrating that the SARS-CoV 7a protein interacts with human Ap4A-hydrolase (asymmetrical diadenosine tetraphosphate hydrolase, EC 3.6.1.17). Ap4A-hydrolase is responsible for metabolizing the "allarmone" nucleotide Ap4A and therefore likely involved in regulation of cell proliferation, DNA replication, RNA processing, apoptosis and DNA repair. The interaction between 7a and Ap4A-hydrolase was identified using yeast two-hybrid screening. The interaction was confirmed by co-immunoprecipitation from cultured human cells transiently expressing V5-His tagged 7a and HA tagged Ap4A-hydrolase. Human tissue culture cells transiently expressing 7a and Ap4A-hydrolase tagged with EGFP and Ds-Red2 respectively show these proteins co-localize in the cytoplasm.

The Role of Severe Acute Respiratory Syndrome (SARS)-Coronavirus Accessory Proteins in Virus Pathogenesis

“…How this would be beneficial to the viral life cycle is unclear as the SARS-CoV relies on host cell protein synthesis to replicate viral proteins. Expressed ORF7a also interacts with human small glutamine-rich tetratricopeptide protein [100], human lymphocyte function-associated antigen 1 (LFA-1) on Jurkat cells and with human Ap4A-hydrolase [104]. …”

Design of novel multi-epitope vaccines against severe acute respiratory syndrome validated through multistage molecular interaction and dynamics

“…The ORF 3 b protein plays a crucial role in the upregulation of transcriptional activity during pathogenesis, and hence 3 b is also a potential drug and vaccine design target (Åkerstr€ om et al, 2007;Varshney et al, 2012). The ORF 7a protein plays an important role during the viral replication cycle (Åkerstr€ om et al, 2007;Vasilenko et al, 2010). The ORF 7 b protein plays a crucial role in virus replication as well as enhances virulence (DeDiego et al, 2008;Pfefferle et al, 2009).…”

Crystal structure of wild-type and mutant human Ap4A hydrolase

“…Ap 4 A hydrolase is responsible for metabolizing the ''allarmone'' nucleotide Ap 4 A and is therefore involved in all the above biological processes. Recent evidence further implicates that the SARS-CoV 7a protein interacts with human Ap 4 A-hydrolase and may participate in common pathways leading to cell cycle arrest and apoptosis [15]. Ap 4 A hydrolase belongs to Nudix (nucleoside diphosphate linked to X) hydrolases, a superfamily of Mg 2+ -dependent enzymes which catalyze the hydrolysis of nucleoside diphosphates linked to other moieties, X, and contains the conserved Nudix sequnce GX 5 EX 7 REUXEEXGU (where U represents a bulky aliphatic residue usually Ile, Leu or Val, and X represents any resi-due) [16].…”