The transcript release factor PTRF augments ribosomal gene transcription by facilitating reinitiation of RNA polymerase I

AUTOR(ES)

Jansa, Petr

FONTE

Oxford University Press

RESUMO

Termination of murine rDNA transcription by RNA polymerase I (Pol I) requires pausing of Pol I by terminator-bound TTF-I (transcription termination factor for Pol I), followed by dissociation of the ternary complex by PTRF (Pol I and transcript release factor). To examine the functional correlation between transcription termination and initiation, we have compared transcription on terminator-containing and terminator-less rDNA templates. We demonstrate that terminated RNA molecules are more efficiently synthesized than run-off transcripts, indicating that termination facilitates reinitiation. Transcriptional enhancement is observed in multiple- but not single-round transcription assays measuring either promoter-dependent or promoter-independent Pol I transcription. Increased synthesis of terminated transcripts is observed in crude extracts but not in a PTRF-free reconstituted transcription system, indicating that PTRF-mediated release of pre-rRNA is responsible for transcriptional enhancement. Consistent with PTRF serving an important role in modulating the efficiency of rRNA synthesis, PTRF exhibits pronounced charge heterogeneity, is phosphorylated at multiple sites and fractionates into transcriptionally active and inactive forms. The results suggest that regulation of PTRF activity may be an as yet unrecognized means to control the efficiency of ribosomal RNA synthesis.

Documentos Relacionados

• Eukaryotic transcription termination factor La mediates transcript release and facilitates reinitiation by RNA polymerase III.
• Footprinting of ribosomal RNA genes by transcription initiation factor and RNA polymerase I.
• Cooperative binding of the Xenopus RNA polymerase I transcription factor xUBF to repetitive ribosomal gene enhancers.
• The enhancement of ribosomal transcription by the recycling of RNA polymerase I.
• Sarkosyl block of transcription reinitiation by RNA polymerase II as visualized by the colliding polymerases reinitiation assay.