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SARS-CoV-2 Morphology, Genomic Organisation and Lifecycle
Published in Srijan Goswami, Chiranjeeb Dey, COVID-19 and SARS-CoV-2, 2022
Srijan Goswami, Ushmita Gupta Bakshi
Studies have shown that the replication cycle of coronaviruses undergoes two important biochemical mechanisms. First, ribosome frameshifting during genome translation. This can be observed during the initial production of polyproteins, which are actually used to generate most of the protein machinery of the replisome or transcriptosome. Second, synthesis of both genomic and multiple subgenomic RNA species.
The mitochondrial DNA depletion syndromes: mitochondrial DNA polymerase deficiency
Published in William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop, Atlas of Inherited Metabolic Diseases, 2020
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop
Other candidate defects lie in the tissue-specific expression of chaperonins required for accurate trafficking of nuclear gene products, such as the polymerase components of the replisome (Figure 56.5), and components of the respiratory chain into mitochondria.
Misconnecting the dots: altered mitochondrial protein-protein interactions and their role in neurodegenerative disorders
Published in Expert Review of Proteomics, 2020
Mara Zilocchi, Mohamed Taha Moutaoufik, Matthew Jessulat, Sadhna Phanse, Khaled A. Aly, Mohan Babu
Mt biogenesis and mitophagy are two additional mt endeavors that control mt mass and functions, and alterations of this process are also involved in NDs [3,11,23]. First, mt biogenesis implies the division of preexisting organelles through the classical trio of mtDNA replication, transcription and translation. This process accommodates increased energy demands in various brain tissues, and reports show plummeting mt biogenesis with age [98]. The DNA polymerase γ (POLG) acts together with other replisome components, such as TWINKLE mtDNA helicase (also known as PEO1), mt single-stranded DNA-binding protein (mtSSB) and mt DNA ligase III to initiate the replication of mtDNA [99]. ER-mt contact sites that are spatially linked to a subset of nucleoids and marked selectively by mtDNA polymerase are engaged with mtDNA replication and division to distribute newly replicated mtDNA in human cells, suggesting a functional interdependence between mt-ER dynamics and mt genome maintenance [79].
Biological challenges of phage therapy and proposed solutions: a literature review
Published in Expert Review of Anti-infective Therapy, 2019
Katherine M Caflisch, Gina A Suh, Robin Patel
Phages are viruses (with single- or double-stranded DNA or RNA genomes) that exclusively infect bacteria. Like other viruses, phages lack a complete replisome and must, therefore, assume intracellular infection of a host to propagate. Phages undergo receptor-mediated adsorption to the surface of target bacteria prior to injecting their genetic material into the cytoplasm where bacterial replication machinery is subverted to produce new virions [1]. Phages are released following bacterial lysis, thereafter infecting adjacent hosts. In therapeutic settings, exclusively virulent phages (i.e., those that do not integrate into bacterial genomes) are generally favored over those that can integrate into bacterial genomes due to the predictable time to lysis, and also because host genomic integration and excision of temperate phage risks mobilization or activation of virulence and/or antibiotic resistance genes, and because infection by temperate phages may prevent subsequent phage infection of their bacterial host [2]. A detailed description of the lytic and lysogenic life cycles of phage is found elsewhere [1].
An update on Alpers-Huttenlocher syndrome: pathophysiology of disease and rational treatment designs
Published in Expert Opinion on Orphan Drugs, 2018
POLG1 is responsible for both mtDNA replication, nucleotide proof reading, and repair. POLG1 encodes the catalytic subunit of the heterotrimer replicase consisting of 140 kDa catalytic (α) subunit of the mtDNA POLG1 and two 55 kDA accessory (β) subunits (POLG2). The POLG1 protein has three functional domains (Figure 1). The amino terminal contains the 3ʹ–5ʹ proofreading exonuclease, the middle region is the linker region and binds one of the POLG2 proteins. The carboxyl-terminal end of the protein contains the 5ʹ–3ʹ polymerase activity and the 5ʹ-deoxyribose phosphate lyase activity. One POLG2 protein is bound to the linker region and enhances DNA-binding affinity of the enzyme [27]. The second POLG2 protein binds POLG1 at a distal accessory site and further enhances the polymerization rate of the holoenzyme [27,28]. Even with the intimate interactions of POLG1 and POLG2, there have not been any pathological variants in POLG2 causing AHS. Within the POLG1 protein there are several areas of highly conserved sequence motifs; three within the exonuclease region and three within the polymerase region. The faithful gene expression of these motifs is essential for full enzyme activity [29,30]. There are two conserved motifs within the linker region and are required for full processivity. Processivity is the average number of nucleotides added by the enzyme per association/disassociation with the template DNA [28]. In addition to the POLG trimer, there are other proteins involved in the mtDNA replisome; Twinkle (encoded by TWNK, also known as c10orf2), mitochondrial topoisomerase I, mitochondrial RNA polymerase (mtRNAP), RNas H1 (encoded by RNASEH1), mitochondrial genome maintenance exonuclease I (MGME1), mitochondrial single-stranded DNA-binding protein (mtSSB), DNA ligase III, DNA helicase/nuclease 2 (DNA2), and RNA and DNA flap endonuclease I (FEN1) [31,32].