Yeast ribosomal protein S33 is encoded by an unsplit gene.

The structure of the gene coding for ribosomal protein S33, - a protein which escapes the coordinate control of ribosomal protein synthesis in rna 2 mutant cells -, was determined by sequence analysis. The gene comprises an uninterrupted coding region of 204 nucleotides encoding a protein of 8.9 kD. Like for other yeast ribosomal protein genes that have been sequenced so far, a relatively strong codon bias was observed. By S1 nuclease mapping the 5' end of the S33 mRNA was shown to be located at 11 to 15 nucleotides upstream from the initiation codon.     

Ribosomal protein L4 of Saccharomyces cerevisiae: the gene and its protein.

The sequence of a gene for ribosomal protein L4 of Saccharomyces cerevisiae has been determined. Unlike most ribosomal protein genes of S. cerevisiae this gene has no intron. The single open reading frame predicts that L4 is highly homologous to mammalian ribosomal protein L7a. There appear to be two genes for L4, both of which are active.     

Structural comparison of yeast ribosomal protein genes.

The primary structure of the genes encoding the yeast ribosomal proteins L17a and L25 was determined, as well as the positions of the 5'- and 3'-termini of the corresponding mRNAs. Comparison of the gene sequences to those obtained for various other yeast ribosomal protein genes revealed several similarities. In all split genes the intron is located near the 5'-side of the amino acid coding region. Among the introns a clear pattern of sequence conservation can be observed. In particular the intron-exon boundaries and a region close to the 3'-splice site show sequence homology. Conserved sequences were also found in the leader and trailer regions of the ribosomal protein mRNAs. The 5'-flanking regions of the yeast ribosomal protein genes appeared to contain sequence elements that many but not all ribosomal protein genes have in common, and therefore may be implicated in the coordinate expression of these genes. The amino acid coding sequences of the ribosomal protein genes show a biased codon usage. Like most yeast ribosomal protein molecules, L17a and L25 are particularly basic at their N-terminus.     

The Yeast Omnipotent Suppressor Sup46 Encodes a Ribosomal Protein Which Is a Functional and Structural Homolog of the Escherichia Coli S4 Ram Protein

The accurate synthesis of proteins is crucial to the existence of a cell. In yeast, several genes that affect the fidelity of translation have been identified (e.g., omnipotent suppressors, antisuppressors and allosuppressors). We have found that the dominant omnipotent suppressor SUP46 encodes the yeast ribosomal protein S13. S13 is encoded by two similar genes, but only the sup46 copy of the gene is able to fully complement the recessive phenotypes of SUP46 mutations. Both copies of the S13 genes contain introns. Unlike the introns of other duplicated ribosomal protein genes which are highly diverged, the duplicated S13 genes have two nearly identical DNA sequences of 25 and 31 bp in length within their introns. The SUP46 protein has significant homology to the S4 ribosomal protein in prokaryotic-type ribosomes. S4 is encoded by one of the ram (ribosomal ambiguity) genes in Escherichia coli which are the functional equivalent of omnipotent suppressors in yeast. Thus, SUP46 and S4 demonstrate functional as well as sequence conservation between prokaryotic and eukaryotic ribosomal proteins. SUP46 and S4 are most similar in their central amino acid sequences. Interestingly, the alterations resulting from the SUP46 mutations and the segment of the S4 protein involved in binding to the 16S rRNA are within this most conserved region.     

The untranslated leader of nuclear COX4 gene of Saccharomyces cerevisiae contains an intron.

The nuclear gene for subunit IV of cytochrome oxidase (COX4) in Saccharomyces cerevisiae contains a 342 bp intron which is contained entirely within the 5' leader of the message. Splicing of the intron results in removal of several small open reading frames; subsequently, the COX4 AUG becomes the 5' proximal initiation codon. A strain with an rna2- mutation fails to splice mRNA efficiently at restrictive temperature and was used to map the intron splice junctions by RNase protection. Two major mRNA initiation sites were mapped by primer extension of synthetic oligodeoxynucleotides. The splice junctions and internal TACTAAC box conform to consensus sequences previously determined from other yeast introns. One gene for subunit V of cytochrome oxidase (COX5b) has also been shown to contain an intron. The significance of introns in two nuclear genes encoding subunits of cytochrome oxidase is discussed.