The role of AHA motifs in the activator function of tomato heat stress transcription factors HsfA1 and HsfA2.
Using reporter assays in tobacco protoplasts and yeast, we investigated the function of the acidic C-terminal activation domains of tomato heat stress transcription factors HsfA1 and HsfA2. Both transcription factors contain short, essential peptide motifs with a characteristic pattern of aromatic and large hydrophobic amino acid residues embedded in an acidic context (AHA motifs). The prototype is the AHA1 motif of HsfA2, which has the sequence DDIWEELL. Our mutational analysis supports the important role of the aromatic and large hydrophobic amino acid residues in the core positions of the AHA motifs. The pattern suggests the formation of an amphipathic, negatively charged helix as the putative contact region with components of the basal transcription complex. In support of this concept, proline or positively charged residues in or adjacent to the AHA motifs markedly reduce or abolish their activity. Both AHA motifs of HsfA1 and HsfA2 contribute to activator potential, and they can substitute for each other; however, there is evidence for sequence and positional specificity.
Döring
P
P
Department of Molecular Cell Biology, Biocenter N200, 3OG, Goethe University Frankfurt, Marie Curie Strasse 9, D-60439 Frankfurt, Germany.
Treuter
E
E
Kistner
C
C
Lyck
R
R
Chen
A
A
Nover
L
L
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D018551:Solanum lycopersicum / Q000737:chemistry* / Q000235:genetics; D009154:Mutation; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011487:Protein Conformation; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
D004268:DNA-Binding Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D010940:Plant Proteins; D014157:Transcription Factors