Specialized ribosomes and specific ribosomal protein paralogs control translation of mitochondrial proteins

Abstract

Genome duplication in eukaryotes created paralog pairs of ribosomal proteins (RPs) that show high sequence similarity/identity. However, individual paralogs can confer vastly different effects upon cellular processes, e.g., specific yeast paralogs regulate actin organization, bud site selection, and mRNA localization, although how specificity is conferred is unknown. Changes in the RP composition of ribosomes might allow for specialized translation of different subsets of mRNAs, yet it is unclear whether specialized ribosomes exist and if paralog specificity controls translation. Using translatome analyses, we show that the translation of mitochondrial proteins is highly down-regulated in yeast lacking RP paralogs required for normal mitochondrial function (e.g., <i>RPL1b</i>). Although <i>RPL1a</i> and <i>RPL1b</i> encode identical proteins, Rpl1b-containing ribosomes confer more efficient translation of respiration-related proteins. Thus, ribosomes varying in RP composition may confer specialized functions, and RP paralog specificity defines a novel means of translational control.