ES30L: A large subunit rRNA expansion segment enriched in mammals and birds

Ribosomes, the molecular machines that are central to protein synthesis, have gradually been gaining prominence for their potential regulatory role in translation. Eukaryotic cytosolic ribosomes are typically larger than the bacterial ones, partly due to multi-nucleotide insertions at specific conserved positions in the ribosomal RNAs (rRNAs). Such insertions called expansion segments (ESs) are present primarily on the ribosomal surface, with their role in translation and its regulation remaining under-explored. One such ES in the ribosomal large subunit (LSU) is ES30L, which is observed mostly in mammals and birds among eukaryotes. In this study, we show that ES30L possesses complementarity to many protein-coding transcripts in humans and that the complementarity is enriched around the start codon, indicating a possible role in translation regulation. Further, our in silico analysis analyses and in vitro pull-down assays show that ES30L may bind to secondary structures in the 5’ UTR of several transcripts and RNA binding proteins (RBPs) that are essential for translation. Thus, we have identified a potential regulatory role for ES30L in translation. ### Competing Interest Statement The authors have declared no competing interest.