RPL12 phosphorylation regulates translation during mitosis - pSILAC B cell PRM -

project_description Emerging evidence indicates that heterogeneity in ribosome composition can give rise to specialized functions. Until now, research mainly focused on differences in core ribosomal proteins and associated factors. The impact of posttranslational modifications has not yet been studied systematically. Analyzing ribosome heterogeneity is challenging since individual proteins can be part of different subcomplexes (40S, 60S, 80S and polysomes). Here, we develop polysome proteome profiling (3P) to obtain unbiased proteomic maps across ribosomal subcomplexes. 3P combines extensive fractionation by sucrose gradient centrifugation with quantitative mass spectrometry. The high resolution of the profiles allows us to assign proteins to specific subcomplexes. Phosphoproteomics on 3P fractions reveals that phosphorylation of serine 38 in RPL12 -- a known mitotic CDK1 substrate -- is strongly depleted in polysomes. Follow-up experiments confirm that RPL12 phosphorylation regulates translation of specific subsets of mRNAs during mitosis. Together, our results show that posttranslational modification of ribosomal proteins can regulate translation.