Interaction between proteins containing homeodomains associated to leucine zippers from sunflower

GONZALEZ, D.; VALLE, E.; GAGO, G.; CHAN, R.

BIOCHIMICA ET BIOPHYSICA ACTA, N. GENE STRUCTURE AND EXPRESSION

Elsevier

Año: 1997 vol. 1351 p. 137 - 149

0167-4781

A strategy based on the use of PCR with one degenerate oligonucleotide deduced from conserved sequences and lambdagt10 primers was used to isolate homeobox containing sequences from sunflower stem and root cDNA libraries. Sixdifferent partial cDNAs coding for the first 48 amino acids of homeodomains and amino terminal sequences were analyzedand found to be members of the HD-Zip superfamily, which contain a homeobox linked to a leucine zipper coding region.A full-length cDNA clone, Hahb-10, was isolated and characterized. The leucine zipper portions of Hahb-10 and of thepreviously reported Hahb-1 have been utilized to construct fusions with the N-terminal domain of the lambda repressor.These fusions were tested for their ability to bind to lambda promoters in vivo. The expression of a protein containing anactive dimerization domain, but not capable of DNA binding, exerts a dominant negative effect on the ability ofrepressor-zipper fusions to bind to its target DNA. From these experiments, it was concluded that Hahb-1 and -10, whenco-expressed, form preferentially homodimers. Exchange of conserved threonines and leucines at positions a and d of 1 1both zippers reduces dimerization efficiency and allows the formation of heterodimers, suggesting that these residues are,among others, determinants of the specificity of interaction, most likely through changes in hydrophobic packinginteractions at the dimer interface. The results imply that a great number of interacting molecular entities compose thisprotein superfamily which is presumably involved in regulating plant developmental responses.