Bacterial Genetics and Genomics book Discussion Topic: Chapter 1, question 13
In honor of today, the day my book is released to the world, I have decided to blog on the topic of the very first Discussion Topic in the book. This relates to the Last Universal Common Ancestor (LUCA) before what we recognize now as bacteria, archaea, and eukaryotes and the common features we still see in them. I came across this paper (https://www.jbc.org/content/295/8/2313) by Michael W. Gray and Venkat Gopalan in the Journal of Biological Chemistry called ‘Piece by piece: Building a ribozyme’. It focuses on ribosomes, which are central to translation, and RNase P, which is part of tRNA processing. Both ribosomes and RNase P were present in the LUCA.
Ribosomes and RNase P have in common that they have within them ribozyme activity and this catalytic RNA action is fundamental to their function. Ribozymes are, as described in Bacterial Genetics and Genomics, an RNA with enzymatic activity.
In this paper, the story of how RNAs evolved is built, starting from what is believed to be the oldest of the activities within the ribosome, its peptidyl transferase center. The model discussed in this review looks at how fragments of RNA with different functional domains would have accumulated over evolutionary time to become the rRNA sequences that we see now within the ribosomes. Likewise, for RNase P, which is involved in tRNA 5ˈ maturation, the model discussed proposes the progressive evolutionary addition of functional domains. For both models, the authors draw on the literature and years of experimental work and theoretical work to describe how these processes are likely to have evolved.
In summary, Gray and Gopalan show how the long non-coding RNAs like those present in the large subunit rRNAs and in the RNA subunit of RNase P have evolved from smaller RNAs. The origins of these sequences were, over time, “stitched together” to become what we see in genome sequences today. This both explains the common origin of these ribozymes that are shared amongst the bacteria, archaea, and eukaryotes and also provides for the diversity in the lineages, including the 16S, 23S, and 5S rRNAs in bacteria and archaea compared to the 18S, 28S, 5S, and 5.8S rRNAs in eukaryotes.
For everyone receiving the book today or in the near future – enjoy! For anyone else, check out the CRC Press web page to order, where there is currently a sale on with 20% off books and 35% off ebooks: https://www.crcpress.com/Bacterial-Genetics-and-Genomics/Snyder/p/book/9780815345695