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Alternative mechanisms of transcriptional activation by Rap1p

AuthorsIdrissi, Fátima-Zahra ; García-Reyero, Natàlia; Fernández-Larrea, Juan B.; Piña, Benjamín
Issue Date17-May-2001
PublisherAmerican Society for Biochemistry and Molecular Biology
CitationJournal of Biological Chemistry 276(28): 26090-26098 (2001)
AbstractSingle Rap1p DNA-binding sites are poor activators of transcription of yeast minimal promoters, even when fully occupied in vivo. This low efficiency is due to two independent repression mechanisms as follows: one that requires the presence of histones, and one that requires Hrs1p, a component of the RNA polymerase II mediator complex. Both repression mechanisms were greatly reduced for constructs with tandemly arranged sites. In these constructs, UASrpg sequences (ACACCCATACATTT) activated better than telomere-like sequences (ACACCCACACACCC) in an orientation-dependent manner. Both mutations in the SWI/SNF complex and a deletion of amino acids 597--629 of Rap1p (Tox domain) decreased synergistic effects of contiguous telomeric sites. Conversely, deletion of amino acids 700--798 of Rap1p (Sil domain) made UASrpg and telomeric sites functionally indistinguishable. We propose that the Sil domain masks the main transactivation domain of Rap1p in Rap1p-telomere complexes, where the Tox domain behaves as a secondary activation domain, probably by interacting with chromatin-remodeling complexes. Rap1p DNA-binding sites in ribosomal protein gene promoters are mainly UASrpg-like; their replacement by telomeric sequences in one of these promoters (RPS17B) decreased transcription by two-thirds. The functional differences between UASrpgs and telomeric sequences may thus contribute to the differential expression of Rap1p-regulated promoters in vivo.
Description9 pages, 6 figures, 3 tables.-- PMID: 11358963 [PubMed].-- Printed version published Jul 13, 2001.
Publisher version (URL)http://dx.doi.org/10.1074/jbc.M101746200
Appears in Collections:(IDAEA) Artículos
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