ePortfolio Cell Bio: Fall 20219: Lydia Hames




Scientific Literacy Paper
MitoRibo-Tag Mice
MitoRiboTag mice as a versatile tool to study mitoribosome composition and the mitoribosome-interactome in different mouse tissues in vivo As mitoribosome assembly and translation coordination in mitochondria strongly diverge from those in bacteria or the eukaryotic cytosol, it is expected that several mitochondrial-specific translation factors and MIPs have been acquired to assist in these processes. Mitochondria are semi-autonomous eukaryotic cell organelles with important roles in key cellular processes, for example, iron-sulfur cluster biosynthesis and oxidative phosphorylation (OXPHOS; Westermann, 2010). Mammalian mtDNA is a compact 16.6 kb circular genome that encodes two rRNAs, 22 tRNAs, and 11 mRNAs necessary for the production of 13 essential OXPHOS proteins (Ha¨ llberg and Larsson, 2014). To synthesize mtDNA-encoded proteins, mitochondria harbor specialized ribosomes (mitoribosomes) that are 55S ribonucleoprotein complexes formed by two distinct subunits. The 28S small subunit (SSU) consists of 30 nuclear-encoded proteins and the 12S rRNA, whereas the 39S large subunit (LSU) is composed of 52 proteins, the 16S rRNA, and an integrated tRNA (Amunts et al., 2015; Greber et al., 2015; O’Brien and Kalf, 1967a, 1967b). During evolution, mitoribosomes have acquired 36 organelle-specific proteins not found in bacterial ribosomes. I have found directly from the cell resource study we were to review and analyze that MitoRibo-Tag mice are powerful tools for in vivo studies of mitoribosome composition during diverse physiological states, disease, and aging. Some of the disorders associated with mitochondria greatly affect the brain, heart, skeletal muscle and other organs, however decreased mitochondrial function also contributes to the aging and age-associated attributes in human diseases (New research tool for studying mitochondrial disorders and aging). It is summarized by using a combination of biochemical fractionation and immunofluorescence techniques, we demonstrate that PUSL1 is a mitochondrial matrix protein peripherally attached to the mitochondrial inner membrane (Figures 5B, 5C, and S5). Here are a few disorders that are associated with mitochondrial dysfunction; diabetes, Huntington’s disease, certain cancers, and cardiovascular disease. Mitochondria are essential organelles that are primitive for converting cellular energy through oxidative phosphorylation (OXPHOS). Mitochondrial function is tightly linked to the expression of the mitochondrial DNA known as mtDNA. There are many steps from regulating mtDNA expression, to the translation of the mitochondrial ribosome (mitoribosome) in the state of particular interest since it synthesizes essential protein components of the OXPHOS system. Defective mitochondrial translation leads to severe OXPHOS dysfunction, this is a process heavily affecting the human body and it’s processes in pathology and ageing. This article explores and explains the purification of mitoribosomes within the mice tissues and the study of mitoribosomes in vivo we generated “MitoRibo-Tag” that were knock-in mice expressing a FLAG-tagged variant of the mitoribosomal protein Immature colon carcinoma transcript 1 (ICT1). The authors purposes were to try to determine the composition of the mitoribosome from different tissues and investigate and identify putative tissue-specific mitoribosome interacting proteins by label-free quantitative mass spectrometry. Discovering and defining the protein content of the mitoribosome and interacting proteins will contribute to a better understanding of the mitochondrial translation machinery, its assembly processes, functions, and mitochondrial diseases and ageing linked to defective mitochondrial translation (KEYSTONE).
Works Cited:
Jakob D. Busch, Miriam Cipullo, Ilian Atanassov, Ana Bratic, Eduardo Silva Ramos, Thomas Schöndorf, Xinping Li, Sarah F. Pearce, Dusanka Milenkovic, Joanna Rorbach, Nils-Göran Larsson,
MitoRibo-Tag Mice Provide a Tool for In Vivo Studies of Mitoribosome Composition,
Cell Reports,
Volume 29, Issue 6,
2019,
Pages 1728-1738.e9,
ISSN 2211-1247,
(http://www.sciencedirect.com/science/article/pii/S2211124719312847)
Abstract: Summary
Mitochondria harbor specialized ribosomes (mitoribosomes) necessary for the synthesis of key membrane proteins of the oxidative phosphorylation (OXPHOS) machinery located in the mitochondrial inner membrane. To date, no animal model exists to study mitoribosome composition and mitochondrial translation coordination in mammals in vivo. Here, we create MitoRibo-Tag mice as a tool enabling affinity purification and proteomics analyses of mitoribosomes and their interactome in different tissues. We also define the composition of an assembly intermediate formed in the absence of MTERF4, necessary for a late step in mitoribosomal biogenesis. We identify the orphan protein PUSL1, which interacts with a large subunit assembly intermediate, and demonstrate that it is an inner-membrane-associated mitochondrial matrix protein required for efficient mitochondrial translation. This work establishes MitoRibo-Tag mice as a powerful tool to study mitoribosomes in vivo, enabling future studies on the mitoribosome interactome under different physiological states, as well as in disease and aging.
Keywords: mitochondria; mitochondrial biogenesis; mitochondrial DNA; mitochondrial gene expression; ribosome; translation;
Leave a Reply