Ubiquitination of Plant Transcription Factors

Ubiquitin is a highly conserved, ubiquitously expressed eukaryotic protein with immensely important, and diverse regulatory functions. The covalent attachment of ubiquitin molecules to intracellular proteins (referred to as ubiquitination) can influence activity, abundance, or localization. The most prominent function of the ubiquitin is its role in selective proteolysis, as a component of the ubiquitin-proteasome system (UPS). In response to an environmental stimulus or developmental cue, ubiquitination of regulatory proteins can be either promoted or inhibited, leading to increased degradation or stabilization, which results in changes in gene expression. Plants have made extensive use of the proteolytic function of ubiquitin to control transcription by regulating the abundance of transcription factors (TFs). A commonly used mechanism is stimulus-induced stabilization of the TF. This and other modes of ubiquitin-dependent control of TF function will be discussed. The regulation of two TFs, ABI5 and MYC2, will be highlighted.