Drugs in Development
- Adjacent Digital Politics Ltd, Datum House November 2015 Are we standing in our own way on the path to a cure for HIV/AIDS? a commentary written by HC Smith.
- Polevoda, B., MacDougall, W.M., Tun, B.N., Cheung, M., Salter, J.D., Friedman, A.E. and Smith, H.C. (2015) RNA Binding to APOBEC3G Induces the Disassembly of Functional Deaminase Complexes by Displacing ssDNA Substrates. Nucleic Acids Research 43:9434-45 PMC4627094. PMID:26424853
- Salter, J.D., Bennett, R.P., Polevoda, B. and Smith, H.C. (2016) The APOBEC Protein Family United by Structure, Divergent in Function. Trends in Biochemical Sciences, Cell Press. 41:578-94 PMID:27283515
- Polevoda, B., McDougall, W.M., Bennett, R.P., Salter, J.D., Smith, H.C. (2016) Structural and Functional Assessment of APOBEC3G Macromolecule Complexes. Methods in Enzymology 107:10-22 PMID:26988126
- Bennett, R.P., Stewart, R.A., Hogan, P., Ptak, R.G., Mankowski, M.K., Hartman, T.L., Buckheit, R.W., Jr., Snyder, B.A., Salter, J.D., Morales, G.A., Smith, H.C. An analog of camptothecin inactive against Topoisomerase I is broadly neutralizing of HIV-1 through inhibition of Vif-dependent APOBEC3G degradation. Antiviral Research 136:51-9 (2016) PMID:27825797
OyaGen seeks to induce transient and beneficial changes in the protein expression and function in human tissues by involving the editing enzymes in targeting biomedically relevant pathways.
OyaGen’s platform technology encompasses a family of fourteen (14) editing enzymes and the proteins that modulate their activity. The functions of editing enzymes have broad biomedical implications many of these enzymes are unexplored. The enzymes that have been studied are known to affect a range of important functions including antiviral, cancer, immunoglobulin gene rearrangements, inflammation, ion channel function, LDL reduction, neuro-cognitive functions and red blood cell expression in fetal liver.
Intellectual property obtained from several universities have been developed by OyaGen as the basis for assays used in high throughput screening for small molecule drug candidates.
OyaGen is strategically positioned to pursue novel therapeutics using assays for highthroughput screening on five targets affecting Vif and APOBEC3G.———
1. Vif Dimerization Antagonist
OyaGen holds an exclusive license from Thomas Jefferson University (TJU) covering the targeting of the Vif dimerization sequence for the development of anti-HIV drugs. OyaGen has validated the availability of the Vif dimerization domain in living cells and the requirement of Vif dimerization for APOBEC3G distruction and viral infectivity.13 A highthroughput assay in mammalian cells has been developed to identify compounds that inhibit Vif dimerization. An E coli assay based on Vif dimerization has also been established for HTS of Vif dimerization antagonists.
2. & 3. Vif interaction with APOBEC3G
OyaGen holds an exclusive license from the University of Rochester and nonexclusive licenses from Oregon Health Science Center on the interaction of Vif with APOBEC3G and the targeting of this interaction in the pursuit of anti-HIV compounds. A highthroughput assay in mammalian cells has been developed to identify compounds that disrupt Vif:APOBEC3G complexes by binding to either Vif or APOBEC3G.. An E coli assay based on Vif:APOBEC3G interaction has also been established for HTS of Vif:APOBEC complex formation antagonists.
4. Vif dependent polyubiquitination of APOBEC3G
OyaGen holds an exclusive license from the University of Rochester and nonexclusive licenses from Oregon Health Science Center on technology for the expression of functional Vif and its interaction with the ubiquitination machinery. Inhibiting this interaction with small molecules identified through high throughput screening will prevent Vif-dependent polyubiquitination of APOBEC3G and of Vif. This novel intervention will preserve APOBEC3G host anti-viral host defense.
5. APOBEC3G activators
OyaGen holds an exclusive license from the University of Rochester and nonexclusive licenses from Oregon Health Science Center on the interaction of APOBEC3G and RNA and the targeting of this interaction in the pursuit of compounds that will disrupt APOBEC 3G binding to RNA and thereby reactivate APOBEC3G deaminase activity and host defense activity. A high throughput assay based on recombinant macromolecules has been developed to identify these compounds.
The HIV life cycle can be broken down into early and late phases during which viral functions are expressed and/or carried out that are critical for host cell infection and virion production. These functionalities have been targeted by drug discovery efforts and have given rise to the important therpeutics used to treat HIV/AIDS. Cells that are not permissive to HIV infection express APOBEC3G and maintain the enzyme as low molecular mass complex primarily consisting of C-terminal dimers.1-3
The early phase of the HIV life cycle involves viral particles binding to surface receptors on permissive cells and replication of the proviral DNA from the viral RNA genome through reverser transcription. Integration of proviral DNA into the host cell chromosomal DNA is a prerequisite to the expression of virions during the late phase of the HIV life cycle. APOBEC3G in nonpermissive cells binds to nascent single strand proviral genomes during their replication and catalyze dC to dU mutation that will template dG to dA mutations in the coding strand of the HIV genome. These point mutations affect the protein coding capacity of the HIV genome and or the dU transitions lead to degradation of the proviral genomes prior to their integration. 4-6
Vif is expressed in the late phase of the HIV life cycle. Vif binds to Elongin B/C and recruits Culin5 along with the E2 ubiquitin ligase to APOBEC3G. APOBEC3G is degraded along with Vif via the proteosome thereby creating a biological APOBEC3G knockdown.9-12 OyaGen has shown that disrupting Vif dimerization disables Vif’s ability to bind to and destroy APOBEC3G. This enables APOBEC3G to be package with virions as they are assembling by binding to Gag and HIV RNA genomes. 13-15
Activation of T cells makes them permissive to HIV infection and under this circumstance APOBEC3G deaminase activity is inactivated by binding to cellular RNA1-2, 5-6 allowing the incoming viruses to replicate, integrate and express viral proteins. OyaGen high throughtput screening has identified compounds that antagonize APOBEC3G binding to cellular RNAs. These compounds activate A3G deaminase activity in permissive cells and thereby inhibit viral replication of incoming virus.