A conserved upstream element is essential for transcription of the Leishmania tarentolae mini-exon gene.
AUTOR(ES)
Saito, R M
RESUMO
We demonstrate that the mini-exon genes of Leishmania tarentolae are individually transcribed by an enzyme pharmacologically identified as RNA polymerase II. To study transcription in these ancient eukaryotes, a stable transformation assay using an episomal mini-exon gene was developed. The introduced mini-exon gene, which had been marked with a 40 bp tag, yielded the predicted tagged transcript. An upstream cis-acting element that was essential for transcription of the mini-exon gene was identified by site-directed mutagenesis. Block substitution mutagenesis of the -1 to +9 and +10 to +19 regions of the exon results in 20- to 100-fold decreased levels of the tagged transcript in steady-state RNA. However, since these two mutations resulted in only a 2- to 3-fold decrease in nascent RNA levels, steady-state levels appear to be affected greatest by the stability of the resulting transcript. In contrast, mutation of the -67/-58 region resulted in undetectable levels of both steady-state and nascent RNA from the introduced gene. We conclude, therefore, that this upstream element, which is highly conserved in all Leishmania species, is a component of the mini-exon gene promoter.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=395504Documentos Relacionados
- Diagnosis of Kala-Azar by Nested PCR Based on Amplification of the Leishmania Mini-Exon Gene
- Discontinuous transcription in Leptomonas seymouri: presence of intact and interrupted mini-exon gene families.
- The structure and transcription of an element interspersed between tandem arrays of mini-exon donor RNA genes in Trypanosoma brucei.
- In vivo recognition of a vertebrate mini-exon as an exon-intron-exon unit.
- The monogenetic kinetoplastid protozoan, Crithidia fasciculata, contains a transcriptionally active, multicopy mini-exon sequence.