Small interfering peptides as a novel way of transcriptional control.

Transcription factors are key components of transcriptional regulatory networks governing virtually all aspects of plant growth and developmental processes. Their activities are regulated at various steps, including gene transcription, posttranscriptional mRNA metabolism, posttranslational modifications, nucleocytoplasmic transport, and controlled proteolytic cleavage of membrane-anchored, dormant forms. Dynamic protein dimerization also plays a critical role in this process. An exquisite regulatory scheme has recently been proposed to modulate the action of transcription factors. Small peptides possessing a protein dimerization motif but lacking the DNA-binding motif form nonfunctional heterodimers with a group of specific TFs, inhibiting their transcriptional activation activities. Extensive searches for small proteins that have a similar structural organization in the databases revealed that small peptide-mediated transcription control is not an exceptional case but would be a regulatory mechanism occurring widespread in the Arabidopsis genome.