Identification of a Drosophila 60S ribosomal protein

We have previously reported the cloning and sequencing of a cDNA from Drosophila (DL43; GenBank Accession # U40226) which predicts a small protein homologous to a ribosomal protein in yeast and rat. In this study we show that a 330 nucleotide transcript encoding the putative ribosomal protein is expressed in Drosophila Kc cells under normal growth conditions (25 degrees C). This RNA is associated with the translational machinery and is present on polysomes. The DL43 cDNA was transcribed using T7 RNA polymerase and the resulting transcripts translated in a wheat germ extract. SDS/PAGE analysis of the in vitro transcribed and translated DL43 cDNA yields a small protein of approximately 9 kDa. Using two-dimensional gelelectrophoresis we have established that the radiolabeled DL43 protein comigrates with a small basic protein in the 60S ribosomal subunit. The electrophoretic mobilities of the in vitro and in vivo synthesized DL43 proteins are indistinguishable providing support for the identity of this protein.