Abstract

A cDNA clone encoding the ribosomal protein S20 has been isolated from the Schizosaccharomyces pombe cDNA library by colony hybridization. The insert contained in the original plasmid pYJ10 was transferred into shuttle vector pRS316 to generate plasmid pYJ11. The cDNA insert of plasmid pYJ11 contains 484 nucleotides and encodes a protein of 118 amino acids with a calculated mass of 13,544 daltons. The deduced amino acid sequence of S. pombe ribosomal protein S20 is very homologous with fruit fly, rat, and budding yeast counterparts. It is also homologous with Xenopus S22 ribosomal protein. S. pombe ribosomal protein S20 appears to be relatively hydrophobic except the C-terminal region. The 728 bp upstream region of the S20 gene was amplified from chromosomal DNA and transferred into the BamHI/EcoRI site of the promoterless b-galactosidase gene of the vector YEp357R, which resulted in fusion plasmid pYS20. The synthesis of b-galactosidase from the fusion plasmid appeared to be the highest in the mid-exponential phase. The S. pombe cells with the fusion plasmid grown at 35oC gave lower b-galactosidase activity than the cells grown at 30oC. Computer analysis showed the consensus sequence CAGTCACA in the upstream regions of various ribosomal protein genes in S. pombe, which would be involved in the coordinated expression of small ibosomal proteins.

• Keywords: cDNA; fission yeast; ribosomal protein S20; regulation; Schizosaccharomyces pombe