The ribosomal protein gene RPS3 is an essential single copy gene of the yeast Saccharomyces cerevisiae.

The communication reports the cloning, sequencing, and analysis of the RPS3 gene from yeast, which codes for the ribosomal protein YS3. Sequence analyses of a 2.45 kb DNA fragment revealed an open reading frame with the potential to code for a 240 amino-acid long protein. The first 20 amino acids display a 90% identity to a 20 amino-acid long protein sequence of yeast ribosomal protein S3, that was obtained by protein sequencing of purified yeast ribosomal proteins. The promoter region of the RPS3 gene contains several upstream conserved sequence elements (UASrpg, T-rich region) that usually regulate transcription of ribosomal protein genes. Northern blot experiments demonstrate that this ORF is transcribed into an approximately 900 nt long mRNA. The major start site of transcription is located near position -20. The RPS3 gene is a single copy gene in yeast. Its disruption yields non viable haploid spores of Saccharomyces cerevisiae.