Analysis of clustered point mutations in the human ribosomal RNA gene promoter by transient expression in vivo.

AUTOR(ES)

Jones, M H

RESUMO

We have mapped the cis regulatory elements required in vivo for initiation at the human rRNA promoter by RNA polymerase I. Transient expression in COS-7 cells was used to evaluate the transcription phenotype of clustered base substitution mutations in the human rRNA promoter. The promoter consists of two major elements: a large upstream region, composed of several domains, that lies between nucleotides -234 and -107 relative to the transcription initiation site and affects transcription up to 100-fold and a core element that lies between nucleotides -45 and +20 and affects transcription up to 1000-fold. The upstream region is able to retain partial function when positioned within 100-160 nucleotides of the transcription initiation site, but it cannot stimulate transcription from distances of greater than or equal to 600 nucleotides. In addition, we demonstrate, using mouse-human hybrid rRNA promoters, that the sequences responsible for human species-specific transcription in vivo appear to reside in both the core and upstream elements, and sequences from the mouse rRNA promoter cannot be substituted for them.

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