Characterization and expression of a Neurospora crassa ribosomal protein gene, crp-7

Abstract

We have isolated and characterized a Neurospora crassa cytoplasmic ribosomal protein gene, named crp-7, which is found upstream of the photolyase gene. The deduced amino-acid sequence of this gene is highly homologous to the YS25 ribosomal protein of Saccharomyces cerevisiae. The crp-7 ORF consists of two exons which are separated by a short intron. The deduced polypeptide contains 87 amino acid residues and has a calculated molecular weight of 9.7 kDa. RFLP mapping showed that the crp-7 gene is located on the right arm of linkage group I. Southern blot hybridization analyses indicated that there is only one copy of the crp-7 gene in the N. crassa genome. Transcriptional elements, the Dde box, the Taq box and the CG element, that have been identified in other N. crassa ribosomal protein genes are observed in the promoter region of the crp-7 gene. The crp-7 mRNA levels were low in conidia and highest in young mycelia during vegetative growth. The mRNA levels of four r-protein genes, including the crp-7 gene, as well as the tef-1 gene encoding translational elongation factor 1α, were raised following the treatment of mycelia with a low concentration of cycloheximide. This indicates that the expression of r-protein genes is under the control of so-called super-induction.