Open AccessTopoisomerases and yeast rRNA transcription: negative supercoiling stimulates initiation and topoisomerase activity is required for elongation.
Author(s) -
Michael C. Schultz,
Steven J. Brill,
Qida Ju,
Rolf Sternglanz,
Ronald H. Reeder
Publication year - 1992
Publication title -
genes and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.136
H-Index - 438
eISSN - 1549-5477
pISSN - 0890-9369
DOI - 10.1101/gad.6.7.1332
Subject(s) - biology , transcription (linguistics) , topoisomerase , dna supercoil , rna polymerase i , rna polymerase , microbiology and biotechnology , abortive initiation , rna polymerase ii , dna , ribosomal rna , rna , biochemistry , promoter , gene , gene expression , dna replication , philosophy , linguistics
Previous work has shown that rRNA synthesis is strongly inhibited in yeast top1-top2 double mutants. Here, we show that inactivation of yeast topoisomerases can have paradoxical effects on transcription by RNA polymerase I. For example, transcription of ribosomal minigenes on extrachromosomal plasmids is greatly stimulated in top1-top2 cells while accumulation of full-length endogenous rRNA is strongly inhibited. We present evidence for a mechanism that can partly account for these opposing effects on transcription. On the one hand, transcription initiation can be stimulated owing to an accumulation of negative superhelicity because polymerase I prefers to initiate on negatively supercoiled templates. Conversely, synthesis of full-length rRNA is inhibited owing to the fact that chain elongation requires a DNA relaxing activity.