Effects of repetitive and non-repetitive rat rDNA enhancer elements on in vivo transcription by RNA polymerases I and II

Asish K. Ghosh, Milko Kermekchiev, Samson T. Jacob*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Previous study has demonstrated that a far upstream 174-bp spacer sequence of the rat rRNA-encoding (rDNA) gene can function as an enhancer in vitro in an orientation- and distance-independent manner [Dixit et al. J. Biol. Chem. 262 (1987) 11616-11622]. To demonstrate that this element can also function in vivo, two rat rDNA-cat plasmids, one with the 174-bp element and the other without this sequence, were constructed and transfected into CHO cells. Primer extension analysis of the transcripts produced after transfection showed that transcription initiation occurred at the +1 site of the rDNA. The 174-bp sequence stimulated the rat poll promoter activity in cis 4-5-fold over the control (with the promoter alone). This RNA polymerase (poll) enhancer also stimulated the mouse metallothionein-I (MT-I) and SV40 promoter activities in vivo, irrespective of its distance and orientation. Further dissection of the 174-bp element revealed that the stimulatory activity on the RNA polymerase II (polII) promoter resides within the 37-bp and 43-bp domains at the 3' end of the 174-bp element. Unlike this spacer enhancer, the 130-bp repeat element (RE) proximal to the rat promoter [Ghosh et al., Gene 125 (1993) 217-222] was unable to modulate the polII promoter activity in vivo. These data show that while the non-repetitive enhancer sequence of rat rDNA is interchangeable for the poll and polII promoters, the RE is poll-specific.

Original languageEnglish (US)
Pages (from-to)271-275
Number of pages5
JournalGene
Volume141
Issue number2
DOIs
StatePublished - Apr 20 1994

Keywords

  • CAT assay
  • Ribosomal RNA
  • primer extension
  • transfection

ASJC Scopus subject areas

  • Genetics

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