The GCN4 leucine zipper can functionally substitute for the heat shock transcription factor’s trimerization domain

作者：Becky Drees, E. Grotkopp, Hillary C.M. Nelson · 发表于：Journal of Molecular Biology · 年份：1997 · DOI：10.1006/jmbi.1997.1283 · 被引用次数：33 · 研究领域：RNA Research and Splicing、Heat shock proteins research、RNA and protein synthesis mechanisms

The heat shock transcription factor (HSF) is the only known sequence-specific, homotrimeric DNA-binding protein. HSF binds to a DNA recognition site called a heat shock element (HSE), which contains varying numbers of nGAAn units ("GAA boxes") arranged in inverted repeats. To investigate the role of trimerization on HSF's DNA-binding properties, we replaced the trimerization domain, which self-assembles to form a three-stranded alpha-helical coiled coil, with the GCN4 leucine zipper, which forms a two-stranded alpha-helical coiled coil. Surprisingly, this substitution did not effect the ability of HSF to function in vivo. Biochemical studies of an HSF-leucine zipper chimera in comparison to an HSF truncation show that the HSF-leucine zipper chimera, though dimeric in solution and dimeric when bound to a two-box HSE, forms a trimeric complex when bound to a three-box HSE. The ability to form trimers depends on the presence of three contiguous GAA boxes present in inverted repeats. The proximity of the leucine zippers due to the orientation of the binding sites suggests that the leucine zippers might be forming a three-stranded coiled coil and several experiments lend support to this model. The ability of the leucine zipper to change oligomeric states in context might explain why the leucine zipper can replace the trimerization domain of HSF in vivo.