Identification and analysis of the start site of ribosomal RNA transcription of Entamoeba histolytica

Abstract

In this article we report the identification of the start site of ribosomal RNA transcription unit of the enteric parasite E. histolytica. We cloned the upstream region of the ribosomal RNA and we defined the 5′ boundary of the transcription unit with nuclear run-on assays. We report that ribosomal transcription starts 2447 bp upstream the SSU ribosomal gene, at an adenosine residue. This data was supported both by S1 mapping and by primer extension analysis; that the mapped site was indeed the transcription start point was demonstrated by RNAse protection of the in vitro capped RNA. Our sequence data around the transcription start point shows two different tandem repeat clusters immediately downstream from the transcription start point.