Asparagine deprivation causes a reversible inhibition of Human Cytomegalovirus acute virus replication

Abstract

13As obligate intracellular pathogens, viruses rely on the host cell machinery to replicate 14 efficiently, with the host metabolism extensively manipulated for this purpose. High 15 throughput siRNA screens provide a systematic approach for the identification of novel host-16 virus interactions. Here, we report a large-scale screen for host factors important for human 17 cytomegalovirus (HCMV), consisting of 6,881 siRNAs. We identified 47 proviral factors and 18 68 antiviral factors involved in a wide range of cellular processes including the mediator 19 complex, proteasome function and mRNA splicing. Focused characterisation of one of the hits, 20 asparagine synthetase (ASNS), demonstrated a strict requirement for asparagine for HCMV 21 replication which leads to an early block in virus replication before the onset of DNA 22 amplification. This effect is specific to HCMV, as knockdown of ASNS had little effect on 23 herpes simplex virus-1 or influenza A virus replication, suggesting the restriction is not simply 24 due to a failure in protein production. Remarkably, virus replication could be completely 25 rescued seven days post-infection with addition of exogenous asparagine, indicating that while 26 virus replication is restricted at an early stage, it maintains the capacity for full replication days 27 after initial infection. This study represents the most comprehensive siRNA screen for the 28 identification of host factors involved in HCMV replication and identifies the non-essential 29 amino acid, asparagine as a critical factor in regulating HCMV virus replication. These results 30 have implications for control of viral latency and the clinical treatment of HCMV in patients. 31Importance 32 HCMV accounts for more than 60% of complications associated with solid organ transplant 33 patients. Prophylactic or preventative treatment with antivirals, such as ganciclovir, reduces 34 the occurrence of early onset HCMV disease. However, late onset disease remains a significant 35 problem and prolonged treatment, especially in patients with suppressed immune systems, 36 greatly increases the risk of antiviral resistance. Very few antivirals have been developed for 37 use against HCMV since the licensing of ganciclovir, and of these, the same viral genes are 38 often targeted, reducing the usefulness of these drugs against resistant strains. An alternative 39 approach is to target host genes essential for virus replication. Here we demonstrate that HCMV 40 replication is highly dependent on levels of the amino acid asparagine and knockdown of a 41 critical enzyme involved in asparagine synthesis results in severe attenuation of virus 42 replication. These results suggest that reducing asparagine levels through dietary restriction or 43 chemotherapeutic treatment could limit HCMV replication in patients. 44 45 of the worldwide population. Although normally asymptomatic in healthy individuals, HCMV 48 infection is a significant cause of morbidity and mortality in immunocompromised populations, 49 individuals with he...

Role of asparagine biosynthesis pathway in Siniperca chuatsi rhabdovirus proliferation

“…Proteins and amino acids play an important role in maintaining body structure and metabolism. The protein requirement of fish is actually a requirement for the mixing ratio of essential and non-essential amino acids (Lee et al, 2019). DMEM medium contains essential amino acids for fish growth to maintain basal cell metabolism (Table 1), these amino acids can be broken down into TCA cycle intermediates into the TCA cycle, but then will not be converted into asparagine and glutamine (De and Zhang, 2018).…”

Host metabolic reprogramming in response to SARS-Cov-2 infection

“…Aspartic acid, asparaginase, and citrulline are also reporter metabolites of infected conditions (Figure 3). Asparaginase is found to be the novel host factor promoting the replication of human cytomegalovirus (HCMV) (Lee et al, 2019). Valine, leucine, and isoleucine (branched chain amino acids, BCAAs) degradation pathway is also downregulated in some cell lines ( Figure 2).…”