Proteomic Analysis of Rodent Ribosomes Revealed Heterogeneity Including Ribosomal Proteins L10-like, L22-like 1, and L39-like

Abstract

Heterogeneity of ribosome structure, due to variations in ribosomal protein composition, has been shown to be of physiological significance in plants and yeast. Mammalian genomics have demonstrated numerous genes that are paralogous to genes encoding ribosomal proteins. Although the vast majority are considered to be pseudogenes, mRNA expression of a few paralogues, such as human ribosomal protein L39-like/L39-2, has been reported. In the present study, ribosomes from the liver, mammary gland, and testis of rodents were analyzed using a combination of two-dimensional gel electrophoresis under radical-free and highly reducing conditions, and mass spectrometry. This system allowed identification of 78 ribosomal proteins and Rack1 from a single gel. The degree of heterogeneity was far less than that reported for plant and yeast ribosomes, and was in accord with published biochemical and genetic data for mammalian ribosomes. Nevertheless, an uncharacterized paralogue of ribosomal protein L22, ribosomal protein L22-like 1, was identified as a minor ribosomal component. Ribosomal proteins L10-like and L39-like, paralogues of ribosomal proteins L10 and L39, respectively, were found in ribosomes only from the testis. Reverse transcription-polymerase chain reaction yielded supportive evidence for specific expression of L10-like and L39-like in the testis. Newly synthesized L39-like is likely to be transported to the nucleolus, where ribosome biosynthesis occurs, and then incorporated into translating ribosomes in the cytoplasm. Heterogeneity of mammalian testicular ribosomes is structurally non-negligible, and may offer valuable insights into the function of the customized ribosome.

Ribosome-omics of the human ribosome

“…RPL10L is expressed almost exclusively in testis, as has been observed biochemically (Sugihara et al 2010). RPL3L is highly expressed in heart and skeletal muscle, but barely at all elsewhere.…”

“…This partially makes up for a substantial reduction in transcripts of RPL3 in those tissues. Because of the overall similarity of the "Like" proteins with their parents, we assume that they can take their place in the ribosome, as has been shown directly for L10L, L22L, and L39L (Sugihara et al 2010;Stadanlick et al 2011). Thus, one of the most intriguing results from the tissue comparisons in Supplemental Tables S6 and S7 is that there are clearly distinct tissue differences in ribosomes, e.g., L3L has likely replaced L3 in ∼25% of the ribosomes of muscle tissue.…”

Depletion of ribosomal protein L8 impairs Drosophila development and is associated with apoptosis

“…The reduction of cyclin B levels causes G 2 arrest by p53-dependent transcriptional repression [34]. Incenp was shown to interact with Aurora B and survivin to form an Aurora B/incenp/survivin complex that is required for normal chromosome segregation [35][36][37]. It was reported that over-expressing survivin reduced p53 protein levels due to enhanced p53 degradation resulting from survivin-mediated inhibition of Mdm2 cleavage by caspases.…”

Influence of Ribosomal Protein L39-L in the Drug Resistance Mechanisms of Lacrimal Gland Adenoid Cystic Carcinoma Cells

“…As a homolog of ribosomal protein L39, ribosomal protein L39-L(RPL39-L) is normally expressed in the human testis and derepressed in multiple cancer cells (Nadano et al, 2002;Sugihara et al, 2010). Even so, the relationship between the function of RPL39-L and cancer cell drug resistance has not been confirmed now.…”