Characterization and regulation of the genes encoding ribosomal proteins L39 and S7 of the human pathogen Candida albicans.

Genes encoding the Candida albicans ribosomal proteins L39 and S7 (RPL39, RPS7) were isolated and sequenced. From RPL39 cDNA a single intron interrupting the fifth codon in the genomic sequence could be deduced. Two homologous RPL39 genes in Saccharomyces cerevisiae contain a single intron in a conserved position. In contrast, C. albicans RPS7 was found to lack an intron, while both S. cerevisiae homologs are interrupted by single introns. The deduced L39 and S7 proteins contained 67% and 83% identical residues compared to the S. cerevisiae homologs. During hyphal induction the RPL39, RPS7 and RPL29 transcript levels increased three- to six-fold relative to ribosomal RNA, while ACT1 and RPS33 control transcripts were not regulated extensively. As suggested by unaltered transcript stabilities during hyphal induction, this regulation occurs on the transcriptional level; a conserved 18 bp palindromic sequence (5'-TTAGGGCTATAGCCCTAA-3'), which is present in the promoter regions of the RPL39 and RPS7 genes, may be involved in regulation.