C2H2 Transcription Factor Family
The C2H2 zinc finger is the classical zinc finger domain. The two conserved cysteines
and histidines co-ordinate a zinc ion. The following pattern describes the zinc finger.
#-X-C-X(1-5)-C-X3-#-X5-#-X2-H-X(3-6)-[H/C] Where X can be any amino acid, and numbers
in brackets indicate the number of residues. The positions marked # are those that are
important for the stable fold of the zinc finger. The final position can be either his
or cys. The C2H2 zinc finger is composed of two short beta strands followed by an alpha
helix. The amino terminal part of the helix binds the major groove in DNA binding zinc
fingers. The accepted consensus binding sequence for Sp1 is usually defined by the
asymmetric hexanucleotide core GGGCGG but this sequence does not include, among others,
the GAG (=CTC) repeat that constitutes a high-affinity site for Sp1 binding to the wt1
promoter.
C2H2 zinc fingers (ZF) display a wide range of functions, from DNA or RNA binding to
the involvement in protein-protein interactions. Therefore ZFPs not only act in
transcriptional regulation, either directly or through site-specific modification
and/or regulation of chromatin, but also participate in RNA metabolism and in other
cellular functions that probably require specific protein contacts of the ZF domain.
Through in silico analysis 176 zinc finger proteins in Arabidopsis thaliana that hence
constitute the most abundant family of putative transcriptional regulators in this
plant were found. Only a minority of 33 A. thaliana zinc finger proteins are conserved
in other eukaryotes. In contrast, the majority of these proteins (81%) are plant
specific. They are derived from extensive duplication events and form expanded
families. We assigned the proteins to different subgroups and families and focused
specifically on the two largest and evolutionarily youngest families (A1 and C1) that
are suggested to be primarily involved in transcriptional regulation. The newly defined
family A1 (24 members) comprises proteins with tandemly arranged zinc finger domains.
Family C1 (64 members), earlier described as the EPF-family in Petunia, comprises
proteins with one isolated or two to five dispersed fingers and a mostly invariant
QALGGH motif in the zinc finger helices. Based on the amino acid pattern in these
helices we could describe five different signature sequences prevalent in C1 zinc
finger domains. We also found a number of non-finger domains that are conserved in
these families.
Analysis of the few evolutionarily conserved zinc finger proteins of A. thaliana
suggests that most of them could be involved in ancient biological processes like RNA
metabolism and chromatin-remodeling. In contrast, the majority of the unique A.
thaliana zinc finger proteins are known or suggested to be involved in transcriptional
regulation. They exhibit remarkable differences in the features of their zinc finger
sequences and zinc finger arrangements compared to animal zinc finger proteins. The
different zinc finger helix signatures found in family C1 may have important
implications for the sequence specific DNA recognition and allow inferences about the
evolution of the members in this family.
4 putative C2H2 TF peptide,
CDS, cDNA sequences,
blast HSP, and multiple sequence alignment in
Legume TFKB. Please more sequences on entry ZF-HD
63 C2H2
protein
and
DNAsequences
with
annotations for soybean in PlantTFDB. Most are partial sequences.
Last updated by Dr. Jeff Chen
on May 28, 2009.