Structure and Expression of Ribosomal RNA Genes from Artemia

Abstract

Stable RNAs in the eukaryotic cell comprise several species all involved in the protein synthesis machinery. They are the 28S, 5.8S and 5S in the large ribosomal subunit, the 18S in the small ribosomal subunit, the 16S and 12S ribosomal RNAs in the mitochondrial ribosomes, and the large families of tRNAs. The study of these RNAs is useful for several reasons. One of them is the construction of evolutionary trees, based on sequence comparisons [1]. A second important point regards their gene structure, at least for the cytoplasmic ribosomal RNA genes. These genes form repeated families, and so the question arises as the whole family is maintained homogeneous, and how mutations are eliminated or fixed at a rate not compatible with selective pressure mechanisms [2]. The structure of the intergenic spacer, made up from small repetitions, also poses questions about the initiation of transcription, in a system where transcription is almost species-specific [3]. It is in this direction that we are approaching the study of these genes in Artemia. Studies on this crustacean could help to fill a gap in molecular evolution, where “arthropod” almost always means “insect”.