SACCHAROMYCES-CEREVISIAE RIBOSOMAL-PROTEIN L37 IS ENCODED BY DUPLICATE GENES THAT ARE DIFFERENTIALLY EXPRESSED

A duplicate copy of the RPL37A gene (encoding ribosomal protein L,37) was cloned and sequenced. The coding region of RPL37B is very similar to that of RPL37A, with only one conservative amino-acid difference. H owever, the intron and flanking sequences of the two genes are extreme ly dissimilar. Disruption experiments indicate that the two loci are n ot functionally equivalent: disruption of RPL37B was insignificant, bu t disruption of RPL37A severely impaired the growth rate of the cell. When both RPL37 loci are disrupted, the cell is unable to grow at all, indicating that rpL37 is an essential protein. The functional dispari ty between the two RPL37 loci could be explained by differential gene expression. The results of two experiments support this idea:,gene fus ion of RPL37A to a reporter gene resulted in six-fold higher mRNA leve ls than was generated by the same reporter gene fused to RPL37B, and a modest increase in gene dosage of RPL37B overcame the lack of a funct ional RPL37A gene.