Why should we care about tRNA modification?
Transfer RNA (tRNA) is at the heart of translation — the process at which the genetic code of an organism is deciphered into functional machines, i.e. proteins. In this process, the tRNA molecules work as adapters that proofread the code and, upon a successful match, add the correct amino acids, i.e. the building blocks that make up proteins. For this intricate process to function correctly, tRNA molecules need to be chemically modified at key positions of the molecule. This is achieved by specialized tRNA modification enzymes acting alone or as part of complex pathways. These post-transcriptional modifications provide structural integrity to the tRNA molecule and more importantly, they regulate the accuracy and speed of translation.
Despite their crucial role in a core function of life, we are only beginning to understand the vast implications of tRNA modification and the complexity of the underlying mechanisms. We know that in microorganisms, such as bacteria and yeast, tRNA modifications are seldom required when growth conditions are optimal. However, once a cell with an aberrant tRNA modification profile encounters any form of stress, severe problems in translation, protein homeostasis, stress response pathways etc. start to emerge. As organismal complexity increases, so does the severity of the implications. For example, a fault in only one mitochondrial tRNA modifying enzyme gives rise to severe developmental disorders in humans, whereas problems in amino acid charging manifest as neurodegenerative diseases. Moreover, incorrect regulation of RNA modifying enzymes has been associated with breast cancer and various other forms of cancer.
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