RNA-seq transcriptomic analysis reveals that ribosomal proteins are not the most highly expressed proteins

Ribosomal proteins are constituent proteins of the ribosome, and thus, should enjoy a relatively high level of expression in most cells. This dovetails with their role as housekeeping proteins. However, the transcriptional picture obtained by RNA-seq analysis of many bacterial species revealed that ribosomal proteins do not typically rank amongst the top ten most highly expressed genes. Only in rare cases such as that with Vibrio chloerae do ribosomal proteins dominate the top ten list of most highly expressed genes in a cell. From a theoretical perspective, the result does not contradict our prevailing view of cell biology. Specifically, ribosomes can reinitiate translation repeatedly and do not have very short half-life; thus, the constituent proteins of ribosome do not need to be repeatedly synthesized at a high level in a cell. Doing it this way saves on metabolic energy and resources at the cellular level. Collectively, as essential proteins of a cell, ribosomal proteins are commonly thought to have a high expression level. However, RNA-seq analysis of a variety of bacterial species revealed that ribosomal proteins do not frequently rank amongst the top ten most highly expressed proteins. Such a result dovetails with our view of ribosomal proteins as housekeeping proteins that do not need to be of high expression level given their relatively long half-life.