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Molecular and Cellular Biology, November 2008, p. 6709-6719, Vol. 28, No. 21
0270-7306/08/$08.00+0     doi:10.1128/MCB.00703-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Transcription of Multiple Yeast Ribosomal DNA Genes Requires Targeting of UAF to the Promoter by Uaf30{triangledown} ,{dagger}

Robert D. Hontz,1,{ddagger} Sarah L. French,2,{ddagger} Melanie L. Oakes,3 Prasad Tongaonkar,3,4 Masayasu Nomura,3 Ann L. Beyer,2 and Jeffrey S. Smith1*

Department of Biochemistry and Molecular Genetics,1 Department of Microbiology, University of Virginia Health System, School of Medicine, Charlottesville, Virginia 22908,2 Department of Biological Chemistry,3 Department of Pathology and Laboratory of Medicine, University of California, Irvine, Irvine, California 926974

Received 29 April 2008/ Returned for modification 4 August 2008/ Accepted 22 August 2008

Upstream activating factor (UAF) is a multisubunit complex that functions in the activation of ribosomal DNA (rDNA) transcription by RNA polymerase I (Pol I). Cells lacking the Uaf30 subunit of UAF reduce the rRNA synthesis rate by ~70% compared to wild-type cells and produce rRNA using both Pol I and Pol II. Miller chromatin spreads demonstrated that even though there is an overall reduction in rRNA synthesis in uaf30 mutants, the active rDNA genes in such strains are overloaded with polymerases. This phenotype was specific to defects in Uaf30, as mutations in other UAF subunits resulted in a complete absence of rDNA genes with high or even modest Pol densities. The lack of Uaf30 prevented UAF from efficiently binding to the rDNA promoter in vivo, leading to an inability to activate a large number of rDNA genes. The relatively few genes that did become activated were highly transcribed, apparently to compensate for the reduced rRNA synthesis capacity. The results show that Uaf30p is a key targeting factor for the UAF complex that facilitates activation of a large proportion of rDNA genes in the tandem array.

* Corresponding author. Mailing address: Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Jordan Hall, Box 800733, Charlottesville, VA 22908. Phone: (434) 243-5864. Fax: (434) 924-5069. E-mail: jss5y{at}virginia.edu

{triangledown} Published ahead of print on 2 September 2008.

{dagger} Supplemental material for this article may be found at http://mcb.asm.org/.

{ddagger} These authors contributed equally.

Molecular and Cellular Biology, November 2008, p. 6709-6719, Vol. 28, No. 21
0270-7306/08/$08.00+0     doi:10.1128/MCB.00703-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Hontz, R. D., Niederer, R. O., Johnson, J. M., Smith, J. S. (2009). Genetic Identification of Factors That Modulate Ribosomal DNA Transcription in Saccharomyces cerevisiae. Genetics 182: 105-119 [Abstract] [Full Text]  


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