Encyclopedia of Biological Chemistry -contributors' Instructions Proof Corrections Should Be Returned in One Communication to Non-print Items Ribosome Assembly

Ribosomes are macromolecular machines that synthesize all cellular proteins. Ribosome biogenesis requires huge expenditure of cellular energy, and its dysregulation can result in a number of diseases including cancer. In vitro reconstitution experiments of bacterial ribosomal subunits have revealed principles underlying the assembly of ribosomes. These principles are also thought to guide the more complex assembly pathway of eukaryotic ribosomal subunits. In eukaryotes, the pathway of assembly of mature ribosomal subunits involves transcription, modification, folding, and processing of pre-rRNA, along with coordinated binding of ribosomal proteins and assembly factors. As pre-ribosomal intermediates undergo maturation, they are released from the nucleolus to the nucleoplasm and eventually exported to the cytoplasm. It is thought that immediately prior to export of ribosomes, they are subjected to structural proofreading so that incompletely assembled ribosomes do not function in translation. Furthermore, quality-control mechanisms ensure that aberrant pre-ribosomal intermediates and dysfunctional mature ribosomes are targeted for