Cytoplasmic ribosomal protein S15a from Brassica napus: molecular cloning and developmental expression in mitotically active tissues.

We have isolated two cDNA clones which appear to encode the 40S ribosomal subunit protein S15a from Brassica napus (oilseed rape). The open reading frame in both clones contains 390 bases, encoding a deduced polypeptide sequence of 130 amino acids (100% homology between clones) with 76% sequence identity to the N-terminal 37 amino acids of the rat ribosomal protein S15a and 80% identity to the S24 polypeptide of yeast. Both the yeast and rapeseed proteins have a net positive charge of +9 and the rapeseed S15a protein has a molecular mass of 14778 Da compared to 14762 Da for the yeast protein. The rapeseed ribosomal protein S15a is encoded by a small multi-gene family with at least two actively transcribed members. A single transcript of ca. 1.0 kb, corresponding to ribosomal protein S15a, is abundant in actively dividing tissues such as apical meristem, flower buds and young leaves and less abundant in mature stem and fully expanded leaves.