Chance and necessity in the evolution of RNase P

Abstract

RNase P catalyzes 5'-maturation of tRNAs in all three domains of life. This primary function is accomplished by either a ribozyme-centered ribonucleoprotein (RNP) or a protein-only variant (with one to three polypeptides). The large, multicomponent archaeal and eukaryotic RNase P RNPs appear disproportionate to the simplicity of their role in tRNA 5'-maturation, prompting the question of why the seemingly gratuitously complex RNP forms of RNase P were not replaced with simpler protein counterparts. Here, motivated by growing evidence, we consider the hypothesis that the large RNase P RNP was retained as a direct consequence of multiple roles played by its components in processes that are not related to the canonical RNase P function.

Keywords: RNase MRP; RNase P; evolution; ribonucleoprotein.

FIGURE 1.

Diversity of the ribonucleoprotein variants of RNase P, and inventory of the multifunctional protein subunits of archaeal/eukaryal RNase P. Overlaid on the secondary structure of the respective RNA subunit are the different RNase P protein subunits. The approximate placement of the protein subunits is based on data reported elsewhere (Tsai et al. 2006; Pulukkunat and Gopalan 2008; Xu et al. 2009; Chen et al. 2010; Reiter et al. 2010; Hipp et al. 2012; Khanova et al. 2012; Fagerlund et al. 2015; Lai et al. 2017). For subunits that have been demonstrated to have roles other than RNase P catalysis, these are indicated using one- or two-letter codes (see key for explanation of the codes). Protein sizes are not exact, and the schematic is not drawn to scale.