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PHD finger Edit Wikipedia article
PHD zinc finger. Zinc atoms shown in grey
The PHD finger (Plant Homeo Domain) was discovered in 1993 as a Cys4-His-Cys3 motif in the homeodomain protein HAT3 in Arabidopsis thaliana. The PHD finger motif resembles the metal binding RING domain (Cys3-His-Cys4) and FYVE domain. It occurs as a single finger, but often in clusters of two or three, and it also occurs together with other domains, such as the chromodomain and the bromodomain.
The PHD finger, approximately 50-80 aminoacids in length, is found in more than 100 human proteins. Several of the proteins it occurs in are found in the nucleus, and are involved in chromatin-mediated gene regulation. The PHD finger occurs in proteins such as the transcriptional co-activators p300 and CBP, Polycomb-like protein (Pcl), Trithorax-group proteins like ASH1L, ASH2L and MLL, the autoimmune regulator (AIRE), Mi-2 complex (part of histone deacetylase complex), the co-repressor TIF1, the JARID1-family of demethylases and many more.
Structure data on the PHD finger
The NMR structure of the PHD finger from human WSTF (Williams Syndrome Transcription Factor) shows that the conserved cysteines and histidine coordinate two Zn2+ ions. In general, the PHD finger adopts a globular fold, consisting of a two-stranded beta-sheet and an alpha-helix. The region consisting of these secondary structures and the residues involved in coordinating the zinc-ions are very conserved among species. The loop regions I and II are variable and could contribute functional specificity to the different PHD fingers.
Function of the PHD finger
Recently the PHD fingers of some proteins, including ING2, YNG1 and NURF, have been reported to bind to histone H3 tri-methylated on lysine 4 (H3K4me3), while other PHD fingers have tested negative in such assays. Interestingly, a protein called SMCX (or JARID1C) has a PHD finger, which has been reported to bind histone H3 tri-methylated lysine 9 (H3K9me3). Based on these recent publications, binding to tri-methylated lysines on histones may therefore be a property widespread among PHD fingers. Domains that bind to modified histones, are called epigenetic readers as they specifically recognize the modified version of the residue and binds to it. The modification H3K4me3 is associated with the transcription start site of active genes, while H3K9me3 is associated with inactive genes. The modifications of the histone lysines are dynamic, as there are methylases that add methyl groups to the lysines, and there are demethylases that remove methyl groups. The SMCX protein is actually a histone H3 lysine 4 demethylase, which means it is an enzyme that can remove the methyl groups of lysine 4 on histone 3 (making it H3K4me2 or H3K4me1). One can only speculate if the H3K9me3-binding of SMCX PHD domain provides a crosstalk between trimethylation of H3K9 and the demethylation of H3K4me3. Such crosstalks have been suggested earlier with other domains involved in chromatin regulation, and may provide a strictly coordinated regulation.
Another example is the PHD finger of the BHC80/PHF21A protein, which is a component of the LSD1 complex. In this complex, LSD1 specifically demethylates H3K4me2 to H3K4me0, and BHC80 binds H3K4me0 through its PHD finger to stabilize the complex at its target promoters, presumably to prevent further re-methylation. This is the first example of a PHD finger recognizing lysine methyl-zero status.
- Schindler U, Beckmann H et al. (1993) "HAT3-1, a novel Arabidopsis homeodomain protein containing a conserved cystein-rich region", Plant J, 4, 137-150
- Aasland R, Gibson T, Stewart AF (1995) "The PHD finger: implications for chromatin-mediated transcriptional regulation", TIBS, 20, 56-59
- Pascual J, Martinez-Yamout M et al. (2000)," Structure of the PHD Zinc Finger from Human Williams-Beuren Syndrome Transcription Factor", Journal of Molecular Biology, 304, 723-729
- Peña PV, Davrazou1 F, Shi X et al. (2006),"Molecular mechanism of histone H3K4me3 recognition by plant homeodomain of ING2", Nature, 442, 100 - 103
- Li H, Ilin S, Wang W et al. (2006),"Molecular basis for site-specific read-out of histone H3K4me3 by the BPTF PHD finger of NURF", Nature, 442, 91-95
- Iwase S, Lan F (2007),"The X-Linked Mental Retardation Gene SMCX/JARID1C Defines a Family of Histone H3 Lysine 4 Demethylases", Cell, 128, 1-12
- Lan F, Collins RE (2007), "Recognition of unmethylated histone H3 lysine 4 links BHC80 to LSD1-mediated gene repression." Nature, 448, 718-22
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PHD folds into an interleaved type of Zn-finger chelating 2 Zn ions in a similar manner to that of the RING and FYVE domains . Several PHD fingers have been identified as binding modules of methylated histone H3 .
Pascual J, Martinez-Yamout M, Dyson HJ, Wright PE; , J Mol Biol 2000;304:723-729.: Structure of the PHD zinc finger from human williams-beuren syndrome transcription factor PUBMED:11124022 EPMC:11124022
Shi X, Kachirskaia I, Walter KL, Kuo JH, Lake A, Davrazou F, Chan SM, Martin DG, Fingerman IM, Briggs SD, Howe L, Utz PJ, Kutateladze TG, Lugovskoy AA, Bedford MT, Gozani O; , J Biol Chem. 2006; [Epub ahead of print]: Proteome-wide analysis in S. cerevisiae identifies several PHD fingers as novel direct and selective binding modules of histone H3 methylated at either lysine 4 or lysine 36. PUBMED:17142463 EPMC:17142463
External database links
This tab holds annotation information from the InterPro database.
InterPro entry IPR019787
Zinc finger (Znf) domains are relatively small protein motifs which contain multiple finger-like protrusions that make tandem contacts with their target molecule. Some of these domains bind zinc, but many do not; instead binding other metals such as iron, or no metal at all. For example, some family members form salt bridges to stabilise the finger-like folds. They were first identified as a DNA-binding motif in transcription factor TFIIIA from Xenopus laevis (African clawed frog), however they are now recognised to bind DNA, RNA, protein and/or lipid substrates [PUBMED:10529348, PUBMED:15963892, PUBMED:15718139, PUBMED:17210253, PUBMED:12665246]. Their binding properties depend on the amino acid sequence of the finger domains and of the linker between fingers, as well as on the higher-order structures and the number of fingers. Znf domains are often found in clusters, where fingers can have different binding specificities. There are many superfamilies of Znf motifs, varying in both sequence and structure. They display considerable versatility in binding modes, even between members of the same class (e.g. some bind DNA, others protein), suggesting that Znf motifs are stable scaffolds that have evolved specialised functions. For example, Znf-containing proteins function in gene transcription, translation, mRNA trafficking, cytoskeleton organisation, epithelial development, cell adhesion, protein folding, chromatin remodelling and zinc sensing, to name but a few [PUBMED:11179890]. Zinc-binding motifs are stable structures, and they rarely undergo conformational changes upon binding their target.
This entry represents the PHD (homeodomain) zinc finger domain [PUBMED:7701562,PUBMED:], which is a C4HC3 zinc-finger-like motif found in nuclear proteins thought to be involved in chromatin-mediated transcriptional regulation. The PHD finger motif is reminiscent of, but distinct from the C3HC4 type RING finger.
The function of this domain is not yet known but in analogy with the LIM domain it could be involved in protein-protein interaction and be important for the assembly or activity of multicomponent complexes involved in transcriptional activation or repression. Alternatively, the interactions could be intra-molecular and be important in maintaining the structural integrity of the protein. In similarity to the RING finger and the LIM domain, the PHD finger is thought to bind two zinc ions.
More information about these proteins can be found at Protein of the Month: Zinc Fingers [PUBMED:].
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
|Molecular function||protein binding (GO:0005515)|
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Superfamily contains a number of zinc-fingers, of the FYVE/PHD type, which are found in several groups of proteins including myelin-associated oligodendrocytic basic proteins (MOBP) Rabphilins, melanophilins, exophilins and myosin-VIIA and Rab-interacting protein families.
The clan contains the following 9 members:FYVE FYVE_2 PHD PHD_2 RAG2_PHD zf-HC5HC2H zf-HC5HC2H_2 zf-PHD-like zf-piccolo
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Curation and family details
|Author:||Pascual J, Bateman A|
|Number in seed:||92|
|Number in full:||10006|
|Average length of the domain:||49.80 aa|
|Average identity of full alignment:||31 %|
|Average coverage of the sequence by the domain:||6.20 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||24|
|Download:||download the raw HMM for this family|
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There is 1 interaction for this family. More...
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the PHD domain has been found. There are 151 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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