Tomato heat stress transcription factor HsfB1 represents a novel type of general transcription coactivator with a histone-like motif interacting with the plant CREB binding protein ortholog HAC1.
In contrast with the class A heat stress transcription factors (HSFs) of plants, a considerable number of HSFs assigned to classes B and C have no evident function as transcription activators on their own. However, in the following article, we provide evidence that tomato (Lycopersicon peruvianum) HsfB1 represents a novel type of coactivator cooperating with class A HSFs (e.g., with tomato HsfA1). Provided the appropriate promoter architecture, the two HSFs assemble into an enhanceosome-like complex, resulting in strong synergistic activation of reporter gene expression. Moreover, HsfB1 also cooperates in a similar manner with other activators, for example, with the ASF1/2 enhancer binding proteins of the 35S promoter of Cauliflower mosaic virus or with yet unidentified activators controlling housekeeping gene expression. By these effects, HsfB1 may help to maintain and/or restore expression of certain viral or housekeeping genes during ongoing heat stress. The coactivator function of HsfB1 depends on a histone-like motif in its C-terminal domain with an indispensable Lys residue in the center (GRGKMMK). This motif is required for recruitment of the plant CREB binding protein (CBP) ortholog HAC1. HsfA1, HsfB1, and HAC1/CBP form ternary complexes in vitro and in vivo with markedly enhanced efficiency in promoter recognition and transcription activation in plant and mammalian (COS7) cells. Using small interfering RNA-mediated knock down of HAC1 expression in Arabidopsis thaliana mesophyll protoplasts, the crucial role for the coactivator function of HsfB1 was confirmed.
Bharti
Kapil
K
Department of Molecular Cell Biology, Goethe University Frankfurt, D-60439 Frankfurt, Germany.
Von Koskull-Döring
Pascal
P
Bharti
Sanita
S
Kumar
Pravir
P
Tintschl-Körbitzer
Angelika
A
Treuter
Eckardt
E
Nover
Lutz
L
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins; D019556:COS Cells; D050882:CREB-Binding Protein; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004357:Drug Synergism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D006657:Histones / Q000737:chemistry*; D018551:Solanum lycopersicum / Q000235:genetics* / Q000378:metabolism*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011523:Protoplasts / Q000166:cytology / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C000620135:HSFB1 protein, Arabidopsis; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D006657:Histones; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D010940:Plant Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D050882:CREB-Binding Protein