ACADEMIA Letters Halting Coronavirus Replication Kira Smith INTRODUCTION How Coronavirus Enters the Host To date, it is known that the Novel Coronavirus (severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)) penetrates host cells via theangiotensin converting enzyme 2 (ACE2) receptor, by binding to glycoprotein S, with some differences from what happens with SARS-CoV-1. (1) From here, you can draw up a list of currently available interventions or known mechanisms of action toreduce the expression of ACE2 activity, in order to avoid (in whole or in part) the entry of the virus into the subject under attack, but not only that. It is also possible that, by lowering its endoribonucleic activity to reduce the ability of the virus to reproduce. So, let us see what can be done. Angiotensin Converting Enzyme 2 Inhibitors: Direct and Indirect Pathways We assume that ACE inhibitors (Lisinopril, Quinapril, Captopril) do not reduce ACE2 activity, despite being structurally related and traceable in the same organs, ACE2 has opposing biological ef- fects (vasodilatation, bronchodilatation, activity to compensate for physical stresses, as some particular conditions, like hypoxia); some direct ACE2 antagonists are: • The small molecule MLN-4760-B and its isomeric MILN-4760, much more selective and effective; Academia Letters, August 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Kira Smith, kira-smith@mil-med.com Citation: Smith, K. (2021). Halting Coronavirus Replication. Academia Letters, Article 2675. https://doi.org/10.20935/AL2675. 1 • DX600 peptide (and DX-512) that have a nanomolar affinity for ACE2, much more than for ACE (almost null), and competitive and non-competitive inhibition. The effectiveness and selectivity between these two ele- ments are concentration-related, but at the concentration of 10 μM, MLN-4760 was found to have a better activity profile. (2) Sirtuin I Inhibitors as Angiotensin Converting Enzyme 2 and Virus Replication Suppressors There is also the possibility of acting indirectly, through a Sirtuine group protein, 7 enzymes NAD+ dependent, known as Sirtuin 1 (SIRT1). Expression of ACE2 activity varies with binding to the SIRT1 protein, so by inhibiting SIRT1, we lower ACE2 activity. (3) Sirtuine are located in the cellular nucleus (SIRT1, SIRT6 and SIRT7), in the cytoplasm (SIRT2), or in the mitochondria (SIRT3, SIRT4 and SIRTS) and are involved in many cellular functions, such as metabolism, the cell cycle, apoptosis, deoxyribonucleic acid (DNA) repair, etc. Recent studies have found that sirtuine may also have enzymatic functions. They are sensors of changes in the intra- and extracellular environment, generally involved in maintaining human health, but are also implicated in viral replication. Examples of virus replication reduced by Sirtuine inhibitors: • The Tat protein of the human immunodeficiency virus infec- tion (HIV) virus is regulated by SIRT1, whose activity of deacetylase, and vice versa is inhibited by the protein Tat. Thetranscription of HIV is regulated by SIRT1, by means of Tat deacetylase. SIRT1 preserves the defenses of the virus, throughout its evolution, allowing therecycling of the protein Transcriptional transactivators(Tat), which binds to transactivation response RNA structures (TAR), and the continuous prolongation of messenger ribonucleic acid (mRNA) transcription; (4) • SIRT1 inhibition (and sometimes even SIRT2) by minor changes to short interfering RNA (siRNA), is known to cause the decrease in replication of additional viruses: flu strains, ve- sicular stomatitis virus (VSV), Kaposi’s Sarcoma-associated Herpes virus (KSHV), Hepatitis B, Hepatitis Cytomegalovirus (CMV), adenovirus, polyomavirus and in some cases the diseas- es counteract: some types of cancer and Huntington’s Chorea, sometimes in combination with antivirals; • Among the various other viruses that respond by slowing their growth, there is just middle east respiratory syndrome-corona- virus(MERS-Cov). It has been observed Academia Letters, August 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Kira Smith, kira-smith@mil-med.com Citation: Smith, K. (2021). Halting Coronavirus Replication. Academia Letters, Article 2675. https://doi.org/10.20935/AL2675. 2 that SIR2 (SIRT1 is the human correspondent) acts as the proviral of MERS-CoV in yeast, due to interactions between ORF4a and eukaryotic cells. The YDL042C/SIR2 yeast gene is a suppressor of ORF4a function. When SIRT1 is inhibited by either chemical or genetic manipulation, there is a reduction of MERS-CoV replication. Moreover, ORF4a inhibited SIRT1-mediated modulation of NF-κB signaling, demonstrating a functional link between OR- F4a and SIRT1 in mammalian cells. A functional link has been identified between the MERS-CoVORF4a proteins and the YDL042C/SIR2 yeast gene. (5) • Vesicular stomatitis virus (VSV-SARS-St19) infection is medi- ated by SARS-CoV-S protein in an ACE2-dependent manner. VSV-SARS-St19 will be useful for analyzing the function of SARS-CoV-S protein and for developing rapid methods of de- tecting neutralizing antibodies specific for SARS-CoV infection. SIRT1 inhibitors stop the growth of VSV, since the cells’ apoptotic response is reduced in cells affected by VSV. (6) Coronaviruses Self-Defense Mechanism Interacion with SARS-unique domain (SUD) and papain-like pro- tease (PLPRO) against p53. The strategy developed from SARS-CoV and other coronaviruses against host immune recognition system is expressed by a SUD that interacts with its partner cellular E3 ubiquitin ligase ring-finger and CHY zinc-finger domain-containing 1 (RCHY1) and with papain-like protease (PLPRO). The consequence is a down- regulation of p53, involved in the reduction of virus replication. The SARS-CoV papain-like protease is encoded next to SUD within nonstructural protein 3. A SUD-PLPRO fusion interacts with RCHY1 more intensively and causes stronger p53 degradation than SARS-CoVPLPRO alone. (7) How p53 is Important in Coronaviruses Replication The p53protein reduces coronavirus replication, because normalgene activation is involved in the cell’s non-specific antiviral defense system. In cells in which p53 is too low, the rate of coronavirus replication is several orders of magnitude higher than that observed in cells in which the p53 is present. (7, 8) Academia Letters, August 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Kira Smith, kira-smith@mil-med.com Citation: Smith, K. (2021). Halting Coronavirus Replication. Academia Letters, Article 2675. https://doi.org/10.20935/AL2675. 3 CONCLUSION Tenovin-l as Hypothetic Perfect Molecule in the Halt of Replication Tenovin-1 [Formal name: N-[[[4-(acetylamino)phenyl]amino] thioxomethyl-4-(1,1-dimethylethyl)]benzamide] is a small molecule inhibitor of sirtuin 1 and sirtuin 2, (8) an activator of p53, less toxic of Tenovin-6. Tenovin-1 at concentration of 10 μM protects p53 from mdm2-mediated degradation with little effect on p53 synthesis. Histone deacetylase inhibitors like tenovin-1 can also indirectly affect the function of some E3 ubiquitin ligases. Tenovin-6 is an analog of tenovin-1. At 10 μM, this compound is slightly more effective than tenovin-1 at elevating p53activity, but it’s more toxic. REFERENCES 1. Chen Y, Guoa Y, Pana Y, Zhao ZJ. Structure analysis of the recep- tor binding of 2019nCoV. Biochemical and Biophysical Research Com- munications. 2020; 525(1): 135140. doi:10.1016/j.bbrc.2020.02.07 2. Li W, Zhang C, Sui J, Kuhn JH, Moore MJ, Luo S, et al. Re- ceptor and viral determinants of SARS-coronavirus adaptation to human ACE2. EMBOJ. 2005; 24: 1634-1643. doi:10.1038/ sj.emboj.7600640 3. Clarke NE, Belyaev ND, Lambert DW, Turner AJ. Epigenetic regulation of angiotensinconverting enzyme 2 (ACE2) by SIRT1 under conditions of cell energy stress. Clin Sci (Lond). 2014; 126(7): 507-516. doi:10.1042/CS20130291 4. Koyuncu E, Budayeva HG, MitevaYV, Ricci DP, Silhavy TJ, Shenk T, et al. Sirtuins are evolutionarily conserved viral restriction factors. mBio. 2014; 5(6): e02249-14. doi:10.1128/mBio.02249-14 5. Weston S, Matthews KL, Lent R, Vlk A, Haupt R, Kingsbury T, et al. A yeast suppressor screen used to identify mammalian SIRT1 as a proviral factor for Middle East respiratory syndrome coronavirus replication. J Viro!. 2019; 93: e00197-19. doi:10.1128/JV1.0019719 6. Fukushi S, Watanabe R, Taguchi F. Pseudotyped vesicular stoma- titis virus for analysis of virus entry mediated by SARS coronavi- rus spike proteins. In: Cavanagh D, Academia Letters, August 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Kira Smith, kira-smith@mil-med.com Citation: Smith, K. (2021). Halting Coronavirus Replication. Academia Letters, Article 2675. https://doi.org/10.20935/AL2675. 4 eds. SARS- and Other Coronaviruses. Methods in Mo!ecu!ar Bio!ogy (Methods and Protoco!s); Totowa, NJ, USA: Humana Press; 2008. 7. Smith K. Novel Coronavirus. Hypothesis of Treatment with SIRT1 inhibitors. doi: 10.13140/RG.2.2.35123.99365 8. Ma-Lauer Y, Carbajo-Lozoya J, Hein MY, Müller MA, Deng W, Lei J, et al. p53 down-regulates SARS coronavirus replication and is targeted by the SARS-unique domain and PLpro via E3 ubiquitin ligase RCHY1. PNAS. 2016; 113 (35): 201603435. doi:10.1073/pnas.1603435113 Academia Letters, August 2021 ©2021 by the author — Open Access — Distributed under CC BY 4.0 Corresponding Author: Kira Smith, kira-smith@mil-med.com Citation: Smith, K. (2021). Halting Coronavirus Replication. Academia Letters, Article 2675. https://doi.org/10.20935/AL2675. 5