Molecular Genetics and Cell Biology of Yeast and Mammalian Cells

Abstract

Iron and copper are essential transition metals involved in key biological processes, including enzyme co-factors, mitochondrial respiration, and ATP production. Their redox properties make them vital yet potentially harmful, as they can induce radical formation through Fenton chemistry. Consequently, stringent regulation of their cellular levels and compartmentalization is crucial. Iron homeostasis is managed by a network involving transferrin, DMT1, and iron regulatory proteins, while copper homeostasis relies on transporters like CTR1 and chaperones like ATOX1. Both metals are implicated in cell death pathways like ferroptosis and cuproptosis, with iron-induced lipid peroxidation and copper-triggered mitochondrial stress playing significant roles. Lipoic acid is vital for multienzyme complexes involved in oxidative decarboxylation and glycine cleavage. In yeast, copper toxicity related to protein lipoylation was studied using knockout strains of lipoic acid pathway components and the pyruvate dehydrogenase complex. In our study growth tests revealed that lip2∆, lip5∆, and lat1∆ strains were resistant to copper and ES, indicating these deletions block copper-mediated cell death. Further analysis showed lip5∆ strains had lower heme synthesis and iron levels, which were linked to growth defects in the presence of succinyl-acetone. Supplementation with hemin and FeSO4 rescued the growth phenotype in lip5∆ strains, highlighting the critical interplay between copper, iron, lipoylation, and cell viability. Additionally, copper is crucial for cellular processes, but its toxicity necessitates tight regulation. Although previous studies indicated overexpression of YAH1 inferred copper resistance in wild type cells, but in our studies with lipoic acid knockout strains, it revealed a growth defect linked to the pRS415 (LEU2) vector. A genomic library screen identified ATP1 as a suppressor, indicating its role in mitochondrial morphology and growth defect rescue. In another aspect of the research our structural analysis of IRES RNA of BVDV, crucial for cap-independent translation, it adopted a modular structure with three domains, including a tertiary H-type pseudoknot. This pseudoknot is evolutionarily conserved across Pestivirus species, revealed through SHAPE-MaP and computational modeling. In another study we utilized Enhanced darkfield hyperspectral microscopy (EDHM), a non-invasive diagnostic method, to identify human coronavirus strains (HCoV) OC43 and 229E. EDHM captured optical images with spectral and spatial details, revealing unique spectral patterns for HCoV-OC43 and HCoV-229E, differentiating them and detecting infections in mammalian cells.