Ribosomes from Eukaryotes: Genetics

Abstract

INTRODUCTION This review concerns the genes that control the synthesis of eukaryotic ribosomes. Due to the general intractability of animal cells to formal genetic experiments, coupled with the difficulty of obtaining mutants in ribosomal loci, the amount of classical genetic data in this area is rather limited. In compensation, however, the structural genes for the ribosomal RNAs are perhaps the most convenient to manipulate biochemically of any known genes, animal, bacterial or viral. Because of these circumstances, the bulk of this review will be concerned with information gained by techniques other than standard genetics. In this context the word “genetic” has been interpreted broadly to include all information regarding the structure, location, function and inheritance of the genes for eukaryotic ribosomes. Two exceptions to the above generalizations on animal genetics are Drosophila and yeast. The ribosomal genes of these organisms are the subject of separate reviews in this volume (Spear, Drosophila; McLaughlin, yeast) and will not be covered here. In addition, this review is only concerned with nuclear ribosomal genes and will not include literature concerning the rDNA of mitochondria or chloroplasts. Throughout this review ribosomal DNA (rDNA) refers to the DNA containing the genes for 18S and 28S RNA of ribosomes plus spacer sequences; ribosomal RNA (rRNA) refers to the RNA product of rDNA. 5S DNA refers to the DNA coding for the 5S RNA of ribosomes plus spacer sequences. THE GENES FOR 18S AND 28S RIBOSOMAL RNA Chromosomal Location of rDNA The genes for ribosomal RNA are unique...