volume 10 Number 9 1982 Nucleic Ac ids Research The S.8S RNA gene sequence and the ribosomal repeat of Schizosaccharomyces pombe

He have characterized the rRNA gene repeat in Schizosaccharomvcea pombe. This repeat, which does not contain the 5S RNA gene, is found in a 10.lt kb Hindlll DNA fragment. We have determined the nuoleotlde sequences of the JS. pombe 5.8S RNA gene and intergenic spacers from two different 10.4 kb DNA fragments. Analysis of isolated total cellular 5-8S RNA revealed the pre-sence of eight species of 5.8S RNA, differing in the number of nucleotides at the 5'-end. The eight 5.8S RNA species vary in length from 158 to 165 nu-oleotides. Apart from the heterogeneity observed at the 5'-end, the sequence of the eight 5.8S RNA species appears to be identical and is the same se-quence as coded for by the 5.8S genes. The gene sequence shows great homo-logy to the 5.8S RNA genes or S. oerevlslae and N.. crassa. Most of the base differences are confined to the highly variable stem thought to be involved in co-axial helix stacking with the 25S RNA, where base pairing is nearly identical despite the sequence differences. Secondary structure models are examined in light of 5.8S RNA oligonuoleotide conservation across species from yeasts to higher eukaryotes. IMTRODPCTION The generalized eukaryotio rlbosome contains four RNA species designat-ed 5S, 5.8S, 17-18S, and 25-28S (1). The genes encoding the three larger RNAs are found in tandemly reiterated DNA sequences and produce a single transcript which is processed to yield the mature rRNA species (1). 5S RNA genes are generally found independently of the large ribosomal repeat. In £. oerevlslae. however, the 5S gene is found within the ribosomal repeat al-though it is transcribed independently (for review see 2). In £. pombe, the 5S genes are not contained in the repeated DNA segment containing genes for the large rRNA speoies (3-6). In this paper we characterize the ribosomal repeat of 2.- Dombe and report the sequence of the gene for 5.8S RNA and its transcript