Ribosome heterogeneity arising from variable rRNA 2′O methylation (2′O Me) has been proposed as a potential mechanism for translational specialization, but whether such heterogeneity contributes to compartment specific translation remains unknown. Here, we systematically compare the 2′O Me landscapes of cytosolic and endoplasmic reticulum (ER)–associated ribosomes across three human cell types: HEK293 cells, H9-derived neural progenitor cells (NPCs), and neurons differentiated from these NPCs. Using detergent-based fractionation combined with RiboMeth-seq, we generate site-resolved rRNA methylation profiles for each compartment. Within each cell type, cytosolic and ER-associated ribosomes display highly similar 2′O Me patterns, with only modest compartment-specific differences observed at 18S:462 in NPCs and 28S:2043 in neurons. Across all samples, differences in 2′O Me patterns are more pronounced between cell types than between compartments. Together, these findings indicate that 2′O Me does not establish a broad ER-specific methylation signature and is unlikely to be a major determinant of ribosome localization or function at the ER.
Uzun et al. (Tue,) studied this question.