Exploring ribosome mediated translation regulation in mammals

Abstract

Mammalian ribosomes have nearly doubled in size compared to the bacterial ribosomes. This is attributable, in part, to the presence of multi-nucleotide insertions in the ribosomal RNA (rRNA) called Expansion Segments (ESs). Even though ESs were first identified at least four decades ago, we still do not possess any understanding of the variability or function of most of these segments across eukaryotes. Given that ribosomes have been gaining prominence for their potential to actively regulate translation, understanding ESs in this context would be very beneficial.

Hence, we investigated the variability of the large subunit ESs across eukaryotes, which included the presence of species-specific expansions. Further, from our study, we observed that one such expansion called ES30L, was present only in endothermic vertebrates (birds and mammals). This expansion appears as a highly flexible extension from the L1-stalk, which is located on the side of tRNA and mRNA exit sites. Using a combination of computational and experimental approaches, this work highlights aspects by which ES30L can interact with protein-coding transcripts and also proteins that are involved in translation.