Conserved sequences upstream of yeast ribosomal protein genes

Computer analysis has previously revealed the presence of a 12-nucleotide common sequence element (AACATCTGCATGACA; HOMOL1) in the upstream regions of several yeast ribosomal protein genes. By extending the sequence analysis of the 5'-flanking regions of a number of other ribosomal protein genes (including those encoding S10-1, S10-2, S33 and L16-2) we could establish that HOMOL1 occurs upstream of most but not all yeast ribosomal protein genes. Apart from HOMOL1 an additional conserved sequence (ACCCATACATTTA; RPG-box) was detected in front of nearly all yeast ribosomal protein genes, although in some cases it is present in the opposite orientation in the other strand. There seems to be no correlation between the occurrence of one box and that of the other. However when both boxes are present the RPG-box is always located 3' to the HOMOL1-sequence mostly at a distance of only a few nucleotides. A further one-to-one comparison of the upstream regions of several yeast ribosomal protein genes revealed extensive additional sequence homologies that are suggested to be involved in the coordinate control of ribosomal protein gene expression in yeast.