Isolation of tobacco ubiquitin-conjugating enzyme cDNA in a yeast two-hybrid system with tobacco ERF3 as bait and its characterization of specific interaction.

Tobacco ETHYLENE-RESPONSIVE FACTOR3 (ERF3) is a member of the ERF-domain transcription factors and has a transcriptional repressor activity, whereas other ERF proteins show activation activity. To understand the regulation of ERF3-repressor activity, protein(s) were screened which interact with ERF3 in a yeast two-hybrid system. A partial sequence (B8) of NtUBC2, a tobacco ubiquitin-conjugating enzyme was isolated. This B8 specifically interacted with ERF3 in the yeast two-hybrid system. Further analyses revealed that the region unique to ERF3 interacted with B8. The physiological functions of NtUBC2 and the stability of ERF3 are discussed in relation to the regulation of the repression activity of ERF3.