Intracellular distribution and identification of the nuclear localization signals of two plant heat-stress transcription factors.
Similar to heat-stress transcription factors (HSFs) from non-plant sources, HSFA1 and HSFA2 from tomato (Lycopersicon esculentum Mill) contain two conserved clusters of basic amino acid residues (K/R1 and K/R2) which might serve as nuclear localization signal (NLS) motifs. Mutation of either one of them and functional testing of the corresponding proteins in a transient expression assay using tobacco (Nicotiana plumbaginifolia L:) protoplasts gave the following results. Whereas K/R1, positioned in all HSFs at the C-terminus of the DNA-binding domain, had no influence on nuclear import, the K/R1 mutants were impaired in their interaction with the DNA (band-shift assays). In contrast to this, mutants of the K/R2 motif, found 15-20 amino acid residues C-terminal of the oligomerization domain (HR-A/B region), had wild-type activity in DNA-binding but were defective in nuclear import. Thus, for the related tomato HSFA1 and HSFA2 the K/R2 cluster represents the only NLS motif, and in this function it cannot be replaced by K/R1.
Lyck
R
R
Department of Molecular and Cellular Biology, Biocenter J.W. Goethe-University, Frankfrut/Main, Germany.
Harmening
U
U
Höhfeld
I
I
Treuter
E
E
Scharf
K D
KD
Nover
L
L
D000595:Amino Acid Sequence; D001483:Base Sequence; D018744:DNA, Plant; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006361:Heating; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D018744:DNA, Plant; D004268:DNA-Binding Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D010940:Plant Proteins; D014157:Transcription Factors