Maf transcription factors form a distinct subfamily of the basic leucine zipper (bZip) transcription factors []. Maf genes have been identified in a wide range of higher eukaryotes, including both vertebrate and invertebrate species. These proteins are unique among the bZip factors in that they contain a highly conserved extended homology region (EHR), or ancillary DNA binding region, in addition to a typical basic region, and both regions are involved in target DNA sequence recognition. Maf transcription factors regulate tissue-specific gene expression and cell-differentiation in a wide variety of tissues and are also involved in human diseases and oncogenic transformation. Tissue-specific expression invloves Maf binding to Maf-recognition elements (MAREs) in the regulatory regions of target genes, and interacting with other transcription factors.This entry includes the Maf protein from vertebrates and V-MAF from Avian musculoaponeurotic fibrosarcoma virus AS42 [].
Maf transcription factors form a distinct subfamily of the basic leucine zipper (bZip) transcription factors []. Maf genes have been identified in a wide range of higher eukaryotes, including both vertebrate and invertebrate species. These proteins are unique among the bZip factors in that they contain a highly conserved extended homology region (EHR), or ancillary DNA binding region, in addition to a typical basic region, and both regions are involved in target DNA sequence recognition. Maf transcription factors regulate tissue-specific gene expression and cell-differentiation in a wide variety of tissues and are also involved in human diseases and oncogenic transformation. Tissue-specific expression invloves Maf binding to Maf-recognition elements (MAREs) in the regulatory regions of target genes, and interacting with other transcription factors.
This region is found in various leucine zipper transcription factors of the Maf family. These are implicated in the regulation of insulin gene expression [], in erythroid differentiation [], and in differentiation of the neuroretina [].
Maf transcription factors form a distinct family of the basic leucine zipper (bZip) transcription factors. The Maf family is divided into two subclasses, large Mafs (c-maf, mafB, and mafA/L-maf, nrl) and small Mafs (MafF, MafK and MafG). Both subclasses contain leucine-zipper motifs, which allow homodimerisation as well as heterodimerisation with a variety of other bZip proteins. In contrast to the small Mafs, the large Maf proteins contain a transactivator domain in their amino terminus []. The small Maf proteins might contribute to oncogenic processes by participating in antioxidant responses, while large Maf proteins have been directly implicated in carcinogenesis []. This entry represents MafA. MafA plays a critical role in the regulation of crystalline genes and lens development [, ]. It also binds the insulin enhancer element RIPE3b and regulates the insulin gene transcription [, , ].
Maf transcription factors form a distinct family of the basic leucine zipper (bZip) transcription factors. The Maf family is divided into two subclasses, large Mafs (c-maf, mafB, and mafA/L-maf, nrl) and small Mafs (MafF, MafK and MafG). Both subclasses contain leucine-zipper motifs, which allow homodimerisation as well as heterodimerisation with a variety of other bZip proteins. In contrast to the small Mafs, the large Maf proteins contain a transactivator domain in their amino terminus.MafB plays critical roles in a variety of cellular differentiation processes, including in kidney podocytes [], macrophages [, ], and pancreatic islet alpha and beta-cells, which are responsible for the production of the hormones glucagon and insulin respectively. MafB is also expressed in alpha-cells in adult pancreas and is important for their function [, , , ].Mutations in Maf gene cause multicentric carpotarsal osteolysis syndrome (MCTO), which is a rare skeletal disorder, usually presenting in early childhood with a clinical picture mimicking juvenile rheumatoid arthritis [].
Maf transcription factors form a distinct family of the basic leucine zipper (bZip) transcription factors. The Maf family is divided into two subclasses, large Mafs (c-maf, mafB, and mafA/L-maf, Nrl) and small Mafs (MafF, MafK and MafG). Both subclasses contain leucine-zipper motifs, which allow homodimerisation as well as heterodimerisation with a variety of other bZip proteins. In contrast to the small Mafs, the large Maf proteins contain a transactivator domain in their amino terminus.Neural retina-specific leucine zipper protein (Nrl) is a member of the Maf family of transcription factors that regulates the expression of rod-specific genes, including rhodopsin [, , ]. Mutations in Nrl cause retinitis pigmentosa 27 (RP27), which is a retinal dystrophy belonging to the group of pigmentary retinopathies [, ], and retinal degeneration autosomal recessive clumped pigment type (RDCP), which is a retinopathy characterised by night blindness since early childhood, consistent with a severe reduction in rod function [].
Maf transcription factors form a distinct subfamily of the basic leucine zipper (bZip) transcription factors []. Maf genes have been identified in a wide range of higher eukaryotes, including both vertebrate and invertebrate species. These proteins are unique among the bZip factors in that they contain a highly conserved extended homology region (EHR), or ancillary DNA binding region, in addition to a typical basic region, and both regions are involved in target DNA sequence recognition. Maf transcription factors regulate tissue-specific gene expression and cell-differentiation in a wide variety of tissues and are also involved in human diseases and oncogenic transformation. Tissue-specific expression invloves Maf binding to Maf-recognition elements (MAREs) in the regulatory regions of target genes, and interacting with other transcription factors.This entry represents MafF, a small Maf protein (sMaf) that lacks the transcriptional activation domain. It forms homodimers that act as transcriptional repressors. sMafs can also form heterodimers with cap 'n' collar (CNC) proteins (p45 NF-E2, Nrf1, Nrf2, and Nrf3) and also with Bach proteins (Bach1 and Bach2) [].
The Maf protein of Bacillus subtilis shares substantial amino acid sequence identity with Escherichia coli YhdE (previously known as OrfE) []. Maf-like proteins are conserved in bacteria, archaea, and eukaryotes. Maf proteins have been implicated in cell division arrest []. It has also been proposed that they belong to a family of house-cleaning nucleotide hydrolyzing enzymes which prevent the incorporation of noncanonical nucleotides into cellular DNA []. Maf proteins exhibit nucleotide pyrophosphatase activity against canonical and modified nucleotides, which might represent a molecular mechanism for this dual role in cell division arrest and in house-cleaning []. This entry includes pyrophosphatases, such as YhdE and YceF from E. coli. YhdE is a nucleoside triphosphate pyrophosphatase that hydrolyzes dTTP and UTP [, , ]. YceF is a nucleoside triphosphate pyrophosphatase that hydrolyzes 7-methyl-GTP (m7GTP) [].
Transcription factor NF-E2 45kDa subunit (p45/NF-E2) belongs to the CNC (Cap'n'Collar) transcription factor family. It is a subunit of the NF-E2 transcription activator, which regulates a number of erythroid- and megakaryocytic lineage-specific genes []. NF-E2 is a heterodimer consisting of p45 and a small Maf protein []. p45 and a small Maf protein dimerise through their leucine zipper domains to generate a DNA binding domain. The N-terminal domain of p45 contains an activation domain that is important for the biological activity of p45 [].
Maf transcription factors contain a conserved basic region leucine zipper (bZIP) domain, which mediates their dimerisation and DNA binding property []. This entry also includes the DNA binding domain of Skn-1 (); this domain lacks the leucine zipper found in other bZip domains, and binds DNA as a monomer [, ].
Maf transcription factors form a distinct family of the basic leucine zipper (bZip) transcription factors. The Maf family is divided into two subclasses, large Mafs and small Mafs (MafF, MafK []and MafG []). Both subclasses contain leucine-zipper motifs, which allow homodimerisation as well as heterodimerisation with a variety of other bZip proteins. Small Mafs can act as negative regulators of transcription by recruiting transcriptional repressors or by forming homodimers that can then displace active dimers. Small Mafs lack a transactivator domain, but they can also serve as transcriptional activators by dimerising with other (usually larger) basic-zipper proteins and recruiting them to specific DNA-binding sites.The small Mafs (MafF, MafG and MafK) appear to be crucial regulators of mammalian gene expression. Small Mafs are also involved in regulating stress response and detoxification pathways [].
Maf transcription factors form a distinct family of the basic leucine zipper (bZip) transcription factors []. The Maf family is divided into two subclasses, large Mafs and small Mafs (MafF, MafK []and MafG []). Both subclasses contain leucine-zipper motifs, which allow homodimerisation as well as heterodimerisation with a variety of other bZip proteins. Small Mafs can act as negative regulators of transcription by recruiting transcriptional repressors or by forming homodimers that can then displace active dimers. Small Mafs lack a transactivator domain, but they can also serve as transcriptional activators by dimerising with other (usually larger) basic-zipper proteins and recruiting them to specific DNA-binding sites. This entry represents MafG. The p45/MafG heterodimer plays a role in the regulation of erythropoiesis []and may be involved in signal transduction of extracellular H+ []. MAFG is up-regulated in smokers [].
The DNA-binding domain of certain eukaryotic transcription factors displays a distinctive helix-turn-helix (HTH) motif. The MafG basic region-leucine zipper (bZIP) protein and the Caenorhabditis elegans Skn-1 transcription factor share this HTH motif. MafG is a member of the Maf family of proteins, which are a subgroup of bZIP proteins that function as transcriptional regulators of cellular differentiation. Mafs can form either homodimers, or heterodimers with other bZIP proteins through their leucine zipper domains. MafG proteins are small Mafs that lack a putative transactivation domain. The DNA-binding domain of MafG contains the conserved Maf extended homology region (EHR), which is not present in other bZIP proteins. The EHR together with the basic region are responsible for the DNA-binding specificity of Mafs. Skn-1 is a transcription factor that specifies mesodermal development in C. elegans. Skn-1 and MafG share a conserved DNA-binding motif, however Skn-1 lacks the leucine zipper dimerisation domain that is found in all bZIP proteins. Skn-1 acts as a monomer. The DNA-binding domains in MafG []and Skn-1 []share structural similarity, despite a sequence identity of only 25%. The domain fold consists of three (MafG) to four (Skn-1) helices, where the long C-terminal helix protrudes from the domain and binds to DNA. MafG lacks the N-terminal helix of Skn-1. A basic cluster of residues is present on the surface of the domain, which together with the amino acid sequence motif, NXXYAXXCR, forms a DNA-binding surface. MafG and Skn-1 may use a common DNA-binding mode. However, the involvement of helix 2 (H2) in DNA recognition differs between MafG and Skn-1, with two residues at the beginning of H2 in MafG contributing to the unique DNA-binding specificity of Mafs.
The COMPASS complex (complex proteins associated with Set1) is conserved in yeasts and in other eukaryotes up to humans. This entry represents Set1 and its homologues. Set1 is a methyltransferase and the catalytic component of the COMPASS that produces trimethylated histone H3 at Lys(4). The yeast COMPASS (Set1C) complex specifically mono-, di- and trimethylates histone H3 to form H3K4me1/2/3, which subsequently plays a role in telomere length maintenance and transcription elongation regulation [, , ]. In yeasts, the Set1C complex consists of Set1(2), Bre2(2), Spp1(2), Sdc1(1), Shg1(1), Swd1(1), Swd2(1), and Swd3(1) [, , , ].In animals, SETD1A/B are histone methyltransferases that produce mono-, di-, and trimethylated histone H3 at 'Lys-4. However, if 'Lys-9' residue is already methylated, 'Lys-4' will not be. The 'Lys-4' methylation is a tag for epigenetic transcriptional activation [, ]. The animal COMPASS complex is composed of at least the catalytic subunit (SETD1A or SETD1B), WDR5, WDR82, RBBP5, ASH2L/ASH2, CXXC1/CFP1, HCFC1 and DPY30 []. ATXR7, the Arabidopsis homologue to Set1, is required for the expression of the flowering repressors FLC and MADS-box genes of the MAF family [, ]. ATXR7 is also involved in the control of seed dormancy and germination [].
