Maryam Hajikarimlou

Natural peptides derived from plants have been an important source of medical substances for several decades. Due to their mechanism of action, chemical potential, and favourable side effect profile, these peptides represent a safer alternative to synthetic pharmaceutical treatments. In this study, we report the discovery of a natural peptide derived from the Brassica napus (Canola) proteome that exhibits high functional similarity to an artificial intelligence (AI)-generated peptide that is designed to bind to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike 1 (S1) protein receptor-binding domain (RBD) region. The results of a series of experiments including molecular docking simulations, as well as binding and inhibition assays suggest that the natural peptide exhibits functions similar to those of the AI-generated peptide in binding to the RBD region and disrupting its interaction with the human host receptor angiotensin-converting enzyme 2 (ACE2). This study demonstrates the potential of AI-designed peptides to facilitate the identification of natural peptides with similar functional properties.

Understanding SARS-CoV-2 human protein-protein interactions (PPIs) and the host response to infection is essential for developing effective COVID-19 antivirals. However, how the ancestral virus and its variants remodel virus-host protein assemblies in various organ-specific cells and bodily fluids remains unclear. Here, we conduct 639 affinity-purifications by tagging and expressing 28 SARS-CoV-2 and spike proteins from the ancestral virus and four variants in eight cell lines representing five mammalian organs and the immune system. Using mass spectrometry (MS), we identify both known and previously unreported SARS-CoV-2-human PPIs, highlighting similarities and differences across organ- or immune-derived cell lines and virus strains. Besides verifying the cell- and variant-specific PPIs, co-fractionation-MS analysis of COVID-19 patients’ saliva confirm host PPI changes between SARS-CoV-2 strains. We discover that the NSP3 papain-like protease, a secreted protein, binds fibrinogen to induce abnormal blood clotting and interferon-induced proteins to evade host innate immune responses. Leveraging deep learning, we design peptide inhibitors that successfully blocked SARS-CoV-2 and variant replication in human liver cells, reversing virus-induced PPI alterations. Together, these findings provide molecular insights into SARS-CoV-2 biology, uncover reorganized viral-host protein assemblies during infection, and identify potential host therapeutic targets and inhibitors for developing antivirals against SARS-CoV-2 strains.

Translation is a fundamental process in biology, and understanding its mechanisms is crucial to comprehending cellular functions and diseases. The regulation of this process is closely linked to the structure of mRNA, as these regions prove vital to modulating translation efficiency and control. Thus, identifying and investigating these fundamental factors that influence the processing and unwinding of structured mRNAs would be of interest due to the widespread impact in various fields of biology. To this end, we employed a computational approach and identified genes that may be involved in the translation of structured mRNAs. The approach is based on the enrichment of interactions and co-expression of genes with those that are known to influence translation and helicase activity. The in silico prediction found CAF20 and ECM32 to be highly ranked candidates that may play a role in unwinding mRNA. The activities of neither CAF20 nor ECM32 have previously been linked to the translation of PGM2 mRNA or other structured mRNAs. Our follow-up investigations with these two genes provided evidence of their participation in the translation of PGM2 mRNA and several other synthetic structured mRNAs.

Reactive oxygen species (ROS) are among the most severe types of cellular stressors with the ability to damage essential cellular biomolecules. Excess levels of ROS are correlated with multiple pathophysiological conditions including neurodegeneration, diabetes, atherosclerosis, and cancer. Failure to regulate the severely imbalanced levels of ROS can ultimately lead to cell death, highlighting the importance of investigating the molecular mechanisms involved in the detoxification procedures that counteract the effects of these compounds in living organisms. One of the most abundant forms of ROS is H ₂ O ₂ , mainly produced by the electron transport chain in the mitochondria. Numerous genes have been identified as essential to the process of cellular detoxification. Yeast YAP1 , which is homologous to mammalian AP‐1 type transcriptional factors, has a key role in oxidative detoxification by upregulating the expression of antioxidant genes in yeast. The current study reveals novel functions for COX5A and NPR3 in H ₂ O ₂ ‐induced stress by demonstrating that their deletions result in a sensitive phenotype. Our follow‐up investigations indicate that COX5A and NPR3 regulate the expression of YAP1 through an alternative mode of translation initiation. These novel gene functions expand our understanding of the regulation of gene expression and defense mechanism of yeast against oxidative stress.

Maintaining translation fidelity is a critical step within the process of gene expression. It requires the involvement of numerous regulatory elements to ensure the synthesis of functional proteins. The efficient termination of protein synthesis can play a crucial role in preserving this fidelity. Here, we report on investigating a protein of unknown function, YNR069C (also known as BSC5), for its activity in the process of translation. We observed a significant increase in the bypass of premature stop codons upon the deletion of YNR069C. Interestingly, the genomic arrangement of this ORF suggests a compatible mode of expression reliant on translational readthrough, incorporating the neighboring open reading frame. We also showed that the deletion of YNR069C results in an increase in the rate of translation. Based on our results, we propose that YNR069C may play a role in translation fidelity, impacting the overall quantity and quality of translation. Our genetic interaction analysis supports our hypothesis, associating the role of YNR069C to the regulation of protein synthesis.

Mitochondria possess their own DNA (mtDNA) and are capable of carrying out their transcription and translation. Although protein synthesis can take place in mitochondria, the majority of the proteins in mitochondria have nuclear origin. 3′ and 5′ untranslated regions of mRNAs (3′-UTR and 5′-UTR, respectively) are thought to play key roles in directing and regulating the activity of mitochondria mRNAs. Here we investigate the association between the presence of 3′-UTR from OXA1 gene on a prokaryotic reporter mRNA and mitochondrial translation in yeast. OXA1 is a nuclear gene that codes for mitochondrial inner membrane insertion protein and its 3′-UTR is shown to direct its mRNA toward mitochondria. It is not clear, however, if this mRNA may also be translated by mitochondria. In the current study, using a β-galactosidase reporter gene, we provide genetic evidence for a correlation between the presence of 3′-UTR of OXA1 on an mRNA and mitochondrial translation in yeast.

Lithium chloride (LiCl) has been widely researched and utilized as a therapeutic option for bipolar disorder (BD). Several pathways, including cell signaling and signal transduction pathways in mammalian cells, are shown to be regulated by LiCl. LiCl can negatively control the expression and activity of PGM2, a phosphoglucomutase that influences sugar metabolism in yeast. In the presence of galactose, when yeast cells are challenged by LiCl, the phosphoglucomutase activity of PGM2p is decreased, causing an increase in the concentration of toxic galactose metabolism intermediates that result in cell sensitivity. Here, we report that the null yeast mutant strains DBP7∆ and YRF1-6∆ exhibit increased LiCl sensitivity on galactose-containing media. Additionally, we demonstrate that DBP7 and YRF1-6 modulate the translational level of PGM2 mRNA, and the observed alteration in translation seems to be associated with the 5′-untranslated region (UTR) of PGM2 mRNA. Furthermore, we observe that DBP7 and YRF1-6 influence, to varying degrees, the translation of other mRNAs that carry different 5′-UTR secondary structures.

Lithium chloride (LiCl) is a widely used and extensively researched drug for the treatment of bipolar disorder (BD). As a result, LiCl has been the subject of research studying its toxicity, mode of action, and downstream cellular responses. LiCl has been shown to influence cell signaling and signaling transduction pathways through protein kinase C and glycogen synthase kinase-3 in mammalian cells. LiCl's significant downstream effects on the translational pathway necessitate further investigation. In yeast, LiCl is found to lower the activity and alter the expression of PGM2, a gene encoding a sugar-metabolism enzyme phosphoglucomutase. When phosphoglucomutase activity is reduced in the presence of galactose, intermediates of galactose metabolism aggregate, causing cell sensitivity to LiCl. In this study, we identified that deleting the genes PEX11 and RIM20 increases yeast LiCl sensitivity. We further show that PEX11 and RIM20 regulate the expression of PGM2 mRNA at the translation level. The observed alteration of translation seems to target the structured 5′-untranslated region (5′-UTR) of the PGM2 mRNA.

DNA double-strand breaks (DSBs) are the most deleterious form of DNA damage and are repaired through non-homologous end-joining (NHEJ) or homologous recombination (HR). Repair initiation, regulation and communication with signaling pathways require several histone-modifying and chromatin-remodeling complexes. In budding yeast, this involves three primary complexes: INO80-C, which is primarily associated with HR, SWR1-C, which promotes NHEJ, and RSC-C, which is involved in both pathways as well as the general DNA damage response. Here we identify ARP6 as a factor involved in DSB repair through an RSC-C-related pathway. The loss of ARP6 significantly reduces the NHEJ repair efficiency of linearized plasmids with cohesive ends, impairs the repair of chromosomal breaks, and sensitizes cells to DNA-damaging agents. Genetic interaction analysis indicates that ARP6, MRE11 and RSC-C function within the same pathway, and the overexpression of ARP6 rescues rsc2∆ and mre11∆ sensitivity to DNA-damaging agents. Double mutants of ARP6, and members of the INO80 and SWR1 complexes, cause a significant reduction in repair efficiency, suggesting that ARP6 functions independently of SWR1-C and INO80-C. These findings support a novel role for ARP6 in DSB repair that is independent of the SWR1 chromatin remodeling complex, through an apparent RSC-C and MRE11-associated DNA repair pathway.