Abortive initiation by Saccharomyces cerevisiae RNA polymerase III

Bhargava, Purnima ; Kassavetis, George A. (1999) Abortive initiation by Saccharomyces cerevisiae RNA polymerase III Journal of Biological Chemistry, 274 (37). pp. 26550-26556. ISSN 0021-9258

Full text not available from this repository.

Official URL: http://www.jbc.org/content/274/37/26550.abstract

Related URL: http://dx.doi.org/10.1074/jbc.274.37.26550


Promoter escape can be rate-limiting for transcription by bacterial RNA polymerases and RNA polymerase II of higher eukaryotes. Formation of a productive elongation complex requires disengagement of RNA polymerase from promoter-bound eukaryotic transcription factors or bacterial sigma factors. RNA polymerase III (pol III) stably associates with the TFIIIB-DNA complex even in the absence of localized DNA unwinding associated with the open promoter complex. To explore the role that release of pol III from the TFIIIB-DNA complex plays in limiting the overall rate of transcription, we have examined the early steps of RNA synthesis. We find that, on average, only three rounds of abortive initiation precede the formation of each elongation complex and that nearly all pol III molecules escape the abortive initiation phase of transcription without significant pausing or arrest. However, when elongation is limited to 5 nucleotides, the intrinsic exoribonuclease activity of pol III cleaves 5-mer RNA at a rate considerably faster than product release or reinitiation. This cleavage also occurs in the normal process of forming a productive elongation complex. The possible role of nucleolytic retraction in disengaging pol III from TFIIIB is discussed.

Item Type:Article
Source:Copyright of this article belongs to The American Society for Biochemistry and Molecular Biology.
ID Code:66964
Deposited On:28 Oct 2011 10:37
Last Modified:28 Oct 2011 10:37

Repository Staff Only: item control page