An auxiliary peptide required for the function of two activation domains in upstream stimulatory factor 2 (USF2) transcription factor
✍ Scribed by Laurence Gourdon; Anne-Marie Lefrançois-Martinez; Benoît Viollet; Antoine Martinez; Axel Kahn; Michel Raymondjean
- Publisher
- Blackwell Publishing
- Year
- 1997
- Tongue
- English
- Weight
- 514 KB
- Volume
- 1
- Category
- Article
- ISSN
- 1360-7413
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✦ Synopsis
Ubiquitous upstream stimulatory factors (USF1, USF2a and USF2b) are members of the basic‐helix–loop–helix‐leucine‐zipper family of transcription factors that have been shown to be involved in the transcriptional response of the L‐type pyruvate kinase (L‐PK) gene to glucose. To understand the mechanisms of action of the USF2 isoforms, we initiated a series of co‐transfection assays with deletion mutants and Gal4–USF2 fusions. The transactivating efficiency of the different native and mutant factors was determined at similar DNA binding activity. We found that: (i) exons 3‐ and 5‐encoded regions are activation domains, (ii) a modulator domain encoded by exon 4 could be necessary to their additive action, (iii) a hexapeptide encoded by the first 5′ codons of exon 6 is indispensable for transmitting activation due to both exon 3‐ and exon 5‐encoded domains to the transcriptional machinery. Therefore, USF2 presents a modular structure and mediates transcriptional activation thanks to two non‐autonomous activation domains dependent on an auxiliary peptide for expressing their activating potential.