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In molecular biology, a transcription factor (TF) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The function of TFs is to regulate—turn on and off—genes in order to make sure that they are expressed in the desired cells at the right time and in the right amount throughout the life of the cell and the organism. Groups of TFs function in a coordinated fashion to direct cell division, cell growth, and cell death throughout life; cell migration and organization during embryonic development; and intermittently in response to signals from outside the cell, such as a hormone. There are 1500-1600 TFs in the human genome. Transcription factors are members of the proteome as well as regulome.
Gibberellins (GAs) are plant hormones that regulate various developmental processes, including stem elongation, germination, dormancy, flowering, flower development, and leaf and fruit senescence. GAs are one of the longest-known classes of plant hormone. It is thought that the selective breeding of crop strains that were deficient in GA synthesis was one of the key drivers of the "green revolution" in the 1960s, a revolution that is credited to have saved over a billion lives worldwide.
Jasmonate (JA) and its derivatives are lipid-based plant hormones that regulate a wide range of processes in plants, ranging from growth and photosynthesis to reproductive development. In particular, JAs are critical for plant defense against herbivory and plant responses to poor environmental conditions and other kinds of abiotic and biotic challenges. Some JAs can also be released as volatile organic compounds (VOCs) to permit communication between plants in anticipation of mutual dangers.
In molecular genetics, a repressor is a DNA- or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA. An RNA-binding repressor binds to the mRNA and prevents translation of the mRNA into protein. This blocking or reducing of expression is called repression.
E2F is a group of genes that encodes a family of transcription factors (TF) in higher eukaryotes. Three of them are activators: E2F1, 2 and E2F3a. Six others act as suppressors: E2F3b, E2F4-8. All of them are involved in the cell cycle regulation and synthesis of DNA in mammalian cells. E2Fs as TFs bind to the TTTCCCGC consensus binding site in the target promoter sequence.
A basic helix–loop–helix (bHLH) is a protein structural motif that characterizes one of the largest families of dimerizing transcription factors. The word "basic" does not refer to complexity but to the chemistry of the motif because transcription factors in general contain basic amino acid residues in order to facilitate DNA binding.
A leucine zipper is a common three-dimensional structural motif in proteins. They were first described by Landschulz and collaborators in 1988 when they found that an enhancer binding protein had a very characteristic 30-amino acid segment and the display of these amino acid sequences on an idealized alpha helix revealed a periodic repetition of leucine residues at every seventh position over a distance covering eight helical turns. The polypeptide segments containing these periodic arrays of leucine residues were proposed to exist in an alpha-helical conformation and the leucine side chains from one alpha helix interdigitate with those from the alpha helix of a second polypeptide, facilitating dimerization.
A DNA-binding domain (DBD) is an independently folded protein domain that contains at least one structural motif that recognizes double- or single-stranded DNA. A DBD can recognize a specific DNA sequence or have a general affinity to DNA. Some DNA-binding domains may also include nucleic acids in their folded structure.
The PHD finger was discovered in 1993 as a Cys4-His-Cys3 motif in the plant homeodomain proteins HAT3.1 in Arabidopsis and maize ZmHox1a. The PHD zinc 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.
Chalcone synthase or naringenin-chalcone synthase (CHS) is an enzyme ubiquitous to higher plants and belongs to a family of polyketide synthase enzymes (PKS) known as type III PKS. Type III PKSs are associated with the production of chalcones, a class of organic compounds found mainly in plants as natural defense mechanisms and as synthetic intermediates. CHS was the first type III PKS to be discovered. It is the first committed enzyme in flavonoid biosynthesis. The enzyme catalyzes the conversion of 4-coumaroyl-CoA and malonyl-CoA to naringenin chalcone.
Apetala 2(AP2) is a gene and a member of a large family of transcription factors, the AP2/EREBP family. In Arabidopsis thaliana AP2 plays a role in the ABC model of flower development. It was originally thought that this family of proteins was plant-specific; however, recent studies have shown that apicomplexans, including the causative agent of malaria, Plasmodium falciparum encode a related set of transcription factors, called the ApiAP2 family.
DNA-binding protein inhibitor ID-2 is a protein that in humans is encoded by the ID2 gene.
MHC class II regulatory factor RFX1 is a protein that, in humans, is encoded by the RFX1 gene located on the short arm of chromosome 19.
"Basic helix-loop-helix family, member e41", or BHLHE41, is a gene that encodes a basic helix-loop-helix transcription factor repressor protein in various tissues of both humans and mice. It is also known as DEC2, hDEC2, and SHARP1, and was previously known as "basic helix-loop-helix domain containing, class B, 3", or BHLHB3. BHLHE41 is known for its role in the circadian molecular mechanisms that influence sleep quantity as well as its role in immune function and the maturation of T helper type 2 cell lineages associated with humoral immunity.
The B3 DNA binding domain (DBD) is a highly conserved domain found exclusively in transcription factors combined with other domains. It consists of 100-120 residues, includes seven beta strands and two alpha helices that form a DNA-binding pseudobarrel protein fold ; it interacts with the major groove of DNA.
The Basic Leucine Zipper Domain is found in many DNA binding eukaryotic proteins. One part of the domain contains a region that mediates sequence specific DNA binding properties and the leucine zipper that is required to hold together (dimerize) two DNA binding regions. The DNA binding region comprises a number of basic amino acids such as arginine and lysine. Proteins containing this domain are transcription factors.
The Methyl-CpG-binding domain (MBD) in molecular biology binds to DNA that contains one or more symmetrically methylated CpGs. MBD has negligible non-specific affinity for unmethylated DNA. In vitro foot-printing with the chromosomal protein MeCP2 showed that the MBD could protect a 12 nucleotide region surrounding a methyl CpG pair.
LUX or Phytoclock1 (PCL1) is a gene that codes for LUX ARRHYTHMO, a protein necessary for circadian rhythms in Arabidopsis thaliana. LUX protein associates with Early Flowering 3 (ELF3) and Early Flowering 4 (ELF4) to form the Evening Complex (EC), a core component of the Arabidopsis repressilator model of the plant circadian clock. The LUX protein functions as a transcription factor that negatively regulates Pseudo-Response Regulator 9 (PRR9), a core gene of the Midday Complex, another component of the Arabidopsis repressilator model. LUX is also associated with circadian control of hypocotyl growth factor genes PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PHYTOCHROME INTERACTING FACTOR 5 (PIF5).
Ethylene signaling pathway is a signal transduction in plant cells to regulate important growth and developmental processes. Acting as a plant hormone, the gas ethylene is responsible for promoting the germination of seeds, ripening of fruits, the opening of flowers, the abscission of leaves and stress responses. It is the simplest alkene gas and the first gaseous molecule discovered to function as a hormone.
The chlorophyll a/b-binding protein gene, otherwise known as the CAB gene, is one of the most thoroughly characterized clock-regulated genes in plants. There are a variety of CAB proteins that are derived from this gene family. Studies on Arabidopsis plants have shed light on the mechanisms of biological clocks under the regulation of CAB genes. Dr. Steve Kay discovered that CAB was regulated by a circadian clock, which switched the gene on in the morning and off in the late afternoon. The genes code for proteins that associate with chlorophyll and xanthophylls. This association aids the absorption of sunlight, which transfers energy to photosystem II to drive photosynthetic electron transport.
References
- ↑ Finlayson SA (May 2007). "Arabidopsis Teosinte Branched1-like 1 regulates axillary bud outgrowth and is homologous to monocot Teosinte Branched1". Plant Cell Physiol. 48 (5): 667–77. doi:10.1093/pcp/pcm044. PMID 17452340.
- 1 2 3 Cubas P, Lauter N, Doebley J, Coen E (April 1999). "The TCP domain: a motif found in proteins regulating plant growth and development". Plant J. 18 (2): 215–22. doi:10.1046/j.1365-313x.1999.00444.x. PMID 10363373.
- ↑ Kosugi S, Ohashi Y (May 2002). "DNA binding and dimerization specificity and potential targets for the TCP protein family". Plant J. 30 (3): 337–48. doi: 10.1046/j.1365-313x.2002.01294.x . PMID 12000681.
- ↑ Navaud O, Dabos P, Carnus E, Tremousaygue D, Hervé C (July 2007). "TCP transcription factors predate the emergence of land plants". J. Mol. Evol. 65 (1): 23–33. Bibcode:2007JMolE..65...23N. doi:10.1007/s00239-006-0174-z. PMID 17568984. S2CID 2961858.
- ↑ Li C, Potuschak T, Colón-Carmona A, Gutiérrez RA, Doerner P (September 2005). "Arabidopsis TCP20 links regulation of growth and cell division control pathways". Proc. Natl. Acad. Sci. U.S.A. 102 (36): 12978–83. Bibcode:2005PNAS..10212978L. doi: 10.1073/pnas.0504039102 . PMC 1200278 . PMID 16123132.