CHARACTERIZATION OF 5S RIBOSOMAL-RNA GENES FROM MOUSE

In order to characterize the transcriptional regulation of the 5S rRNA genes we have isolated a bona fide gene and a pseudogene from mouse cells. These 5S rRNA genes contain a 12-bp sequence designated as the D-box, located in position -33 to -22 bp, and two Sp1-binding sites in the 5'-flanking region. The D-box is conserved in human and hamster 5S rRNA genes although in slightly different upstream positions. The bona fide mouse 5S rRNA gene was transcribed in a HeLa S-100 extract. The transcriptional activity of this gene was only 50% of that of the human gene, indicating the involvement of species-specific transcription factors and/or polymerases. The pseudogene which contains the D-box, but with position + 25 to + 35 bp deleted, showed no transcriptional activity. Deletion of the D-box in the 5'-flanking sequence abolished transcriptional activity, indicating that this conserved sequence is of importance for gene expression.