TAZ Transcription Factor Family
A novel CaM-binding protein was isolated through protein-protein interaction based
screening of an Arabidopsis cDNA expression library using a 35S calmodulin (CaM)
probe. There are four additional homologs in the Arabidopsis genome with similar
structures: a BTB domain in the N-terminus and a Zf-TAZ domain in the C-terminus.
Hence, they were designated as AtBT1-5 (Arabidopsis thaliana BTB and TAZ domain
protein). CaM-binding experiments revealed that all five AtBTs are CaM-binding
proteins, and their CaM-binding domains were mapped to the C-terminus. AtBT homologs
are also present in rice, but are not present in human, animal, yeast or other
organisms, suggesting that the BTB and TAZ domain proteins are plant-specific. The
AtBT1-smGFP fusion protein expressed in tobacco BY-2 cells showed that AtBT1 targets
the nucleus. Yeast two-hybrid screening using an AtBT1 fragment as bait identified
two interacting proteins (AtBET10 and AtBET9) belonging to the family of fsh/Ring3
class transcription regulators. The BTB domain of the AtBTs is required for the
interaction, and this protein-protein interaction was confirmed by GST pull-down.
AtBET10 also interacts with AtBT2 and AtBT4, and exhibited a transcriptional
activation function in yeast cells. AtBTs exhibit varying responses to different
stress stimuli, but all five genes responded rapidly to H2O2 and salicylic acid (SA)
treatments. These results suggest that AtBTs play a role in transcriptional
regulation, and signal molecules such as Ca2+, H2O2, and SA affect transcriptional
machinery by altering the expression and conformation of AtBTs which interact with
transcriptional activators such as AtBET10.
The TAZ2 (CH3) domain of the transcriptional adapter protein CBP has been implicated
in direct functional interactions with numerous cellular transcription factors and
viral oncoproteins. The solution structure of the TAZ2 domain of murine CBP has been
determined by nuclear magnetic resonance (NMR). The protein adopts a novel helical
fold stabilized by three zinc ions, each of which is bound to one histidine and three
cysteine ligands in HCCC-type motifs. Each zinc-binding site is formed from the
carboxy terminus of an alpha-helix, a short loop, and the amino terminus of the next
alpha-helix. A peptide derived from the N-terminal transactivation domain of p53
binds specifically to one face of the TAZ2 domain. The close similarities between the
TAZ2 and TAZ1 (CH1 domain of CBP/p300) sequences suggest that both domains will adopt
similar three-dimensional structures.
(taken from TOBFAC).
Notes:TAZ is missed in AtTFDB and AtPID for protein protein interaction data.
18 TAZ sequences,
blast HSP, and sequence alignment.
8 putative TAZ TF sequenecs (peptide, CDS, cDNA, sequence alignment )
searched via
blast on zf-TAZ domain.
3 TAZ sequences in PlantTFDB. All are partial
sequences.
Last updated by Dr. Jeff Chen on May 23, 2009.