Effect of mutations in the upstream promoter on the transcription of human5S rRNA genes

The human 5S rRNA gene has a 12-mer external promoter, the D box, localized about 30 bp upstream the coding sequence. By site directed mutagenesis 58 different D box promoter mutants were made. While some mutations in the D b ox allowed full transcription, other mutations decreased the transcriptiona l activity to 20-50% compared to the bona fide gene, showing the importance of this external promoter in transcription initiation. A number of maxi 5S rRNA genes were constructed from bona fide genes and D box mutated clones. Transfection of HeLa cells with maxi 5S rRNA genes showed that the D box i s also important for 5S rRNA gene expression in vivo. Evidence from differe nt eukaryotic cells suggests that expression of 5S rRNA genes is regulated by external promoters in addition to the internal control region. (C) 2001 Elsevier Science B.V. All rights reserved.