Ribosomal protein Rpl22 regulates the splicing of its own transcripts

Saccharomyces cerevisiae is an intron-poor organism with introns present in only 5% of its genes. The most prominent group of intron-containing genes are ribosomal protein (RP) genes. They are highly expressed and most of them are present as two paralogs. Parenteau et al. described the existence of intron- dependent intergenic regulatory circuits controlling expression ratios of RP paralogs. In this project, we did not confirm the regulation in 6 out of 7 tested regulatory circuits. We validated the regulation between RPL22 paralogs. We further showed that Rpl22 protein blocks the pre-mRNA splicing of both paralogs, with RPL22B paralog being more sensitive. Rpl22 protein binds to the stem-loop of RPL22B intron - disruption of the binding domain of Rpl22 proteins leads to loss of interaction. Moreover, the regulation seems to be working the same way in yeast Kluyveromyces lactis, which has only a single RPL22 copy. Overall, these results lead to better understanding of intergenic regulation, which adjusts the expression ratio between functionally different RPL22 paralogs. Key words introns, ribosomal protein genes, Rpl22, RPL22 paralogs, pre-mRNA splicing, Saccharomyces cerevisia