Bharti K, Schmidt E, Lyck R, Heerklotz D, Bublak D, Scharf K D
Department of Molecular Cell Biology, Biocenter N200, 3OG, Goethe-University Frankfurt, Marie-Curie-Str. 9, D-60439 Frankfurt, Germany.
Plant J. 2000 May;22(4):355-65. doi: 10.1046/j.1365-313x.2000.00746.x.
Stress-induced transcription of heat shock proteins (Hsps) in eukaryotes is mediated by a conserved class of transcription factors called heat stress transcription factors (Hsfs). Here we report the isolation and functional characterization of HsfA3, a new member of the Hsf family. HsfA3 was cloned from a tomato heat stress cDNA library by yeast two-hybrid screening, using HsfA1 as a bait. HsfA3 is a single-copy gene with all the conserved sequence elements characteristic of a heat stress transcription factor. The constitutively expressed HsfA3 is mainly found in the cytoplasm under control conditions and in the nucleus under heat stress conditions. Functionally, HsfA3 behaves similarly to the already known members of tomato Hsf family. It is able to substitute yeast Hsf for viability functions and is a strong activator of Hsf-dependent reporter constructs both in tobacco protoplasts and yeast. Finally, similar to the AHA motifs in HsfA1 and HsfA2, the activator function depends on four short peptide motifs with a central tryptophan residue found in the C-terminal domain of HsfA3.
真核生物中热休克蛋白（Hsps）的应激诱导转录由一类保守的转录因子介导，称为热应激转录因子（Hsfs）。在此，我们报告了HsfA3的分离及其功能特性，HsfA3是Hsf家族的一个新成员。通过酵母双杂交筛选，以HsfA1为诱饵，从番茄热应激cDNA文库中克隆出HsfA3。HsfA3是一个单拷贝基因，具有热应激转录因子的所有保守序列元件。组成型表达的HsfA3在对照条件下主要存在于细胞质中，在热应激条件下存在于细胞核中。在功能上，HsfA3的行为与番茄Hsf家族中已知成员相似。它能够替代酵母Hsf发挥生存功能，并且在烟草原生质体和酵母中都是Hsf依赖性报告基因构建体的强激活剂。最后，与HsfA1和HsfA2中的AHA基序类似，激活功能取决于在HsfA3 C末端结构域中发现的四个带有中心色氨酸残基的短肽基序。
