The W box is a
deoxyribonucleic acid (DNA)
cis-regulatory element
''Cis''-regulatory elements (CREs) or ''Cis''-regulatory modules (CRMs) are regions of non-coding DNA which regulate the transcription of neighboring genes. CREs are vital components of genetic regulatory networks, which in turn control morphoge ...
sequence, (T)TGAC(C/T), which is recognized by the family of
WRKY transcription factors.
Functionality and conservation of the W-box element across plant species has been shown by gel shift experiments, random binding site selection, yeast one-hybrid screens and co-transfection assays performed with many different WRKY proteins. ''In silico''-based studies together with functional studies of plant promoters have identified clusters of W-boxes in stress-inducible promoters. The binding of WRKY proteins to W-boxes is a feature of both biotic and abiotic stress responses, together with other plant processes such as germination. It has also been shown that multiple W-boxes have a synergistic effect on transcription.
Almost all WRKY transcription factors bind preferentially to W-boxes, and since their discovery, this has raised the question as to how they show specificity for the promoters of their target genes.
Ciolkowski et al. (2008) showed that although the W-box core is required, adjacent sequences also play a role in determining binding-site preference. Recent evidence suggests that the TGAC core is more degenerate, composed of a
guanine
Guanine () ( symbol G or Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine (uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside is c ...
adenine
Adenine () ( symbol A or Ade) is a nucleobase (a purine derivative). It is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The three others are guanine, cytosine and thymine. Its deri ...
cytosine
Cytosine () ( symbol C or Cyt) is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an ...
(GAC) core, and the upstream thymine and downstream
pyrimidine flanking sequences help dictate recognition by specific WRKY factors.
Basic residues of the WRKY protein domain also are believed to recognize the phosphate backbone of the ''cis''-element.
[
Recently, Yamasaki et al. have determined the solution structure of the C-terminal WRKY domain of Arabidopsis WRKY4 in complex with the W-box DNA by NMR.]
External Links and Useful Resources
WRKY Transcription Factor Family
a
The Arabidopsis Information ResourceThe Rushton Lab
The Somssich LabThe Shen LabSomssich’s list of WRKY-related publicationsEulgem Lab
References
{{Reflist
See also
* G-box
* I-box
*T-box
T-box refers to a group of transcription factors involved in embryonic limb and heart development. Every T-box protein has a relatively large DNA-binding domain, generally comprising about a third of the entire protein that is both necessary a ...
* Z-box
Genes