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Transcription Preinitiation Complex
The preinitiation complex (abbreviated PIC) is a complex of approximately 100 proteins that is necessary for the transcription of protein-coding genes in eukaryotes and archaea. The preinitiation complex positions RNA polymerase II at gene transcription start sites, denatures the DNA, and positions the DNA in the RNA polymerase II active site for transcription. The minimal PIC includes RNA polymerase II and six general transcription factors: TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. Additional regulatory complexes (such as the mediator coactivator and chromatin remodeling complexes) may also be components of the PIC. Assembly A classical view of PIC formation at the promoter involves the following steps: * TATA binding protein (TBP, a subunit of TFIID) binds the promoter, creating a sharp bend in the promoter DNA. ** Animals have some TBP-related factors (TRF; TBPL1/ TBPL2). They can replace TBP in some special contexts. * TBP recruits TFIIA, then TFIIB, to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Figure may refer to: General *A shape, drawing, depiction, or geometric configuration *Figure (wood), wood appearance *Figure (music), distinguished from musical motif *Noise figure, in telecommunication *Dance figure, an elementary dance pattern *A person's figure, human physical appearance Arts *Figurine, a miniature statuette representation of a creature *Action figure, a posable jointed solid plastic character figurine *Figure painting, realistic representation, especially of the human form *Figure drawing *Model figure, a scale model of a creature Writing *figure, in writing, a type of floating block (text, table, or graphic separate from the main text) *Figure of speech, also called a rhetorical figure *Christ figure, a type of character * in typesetting, text figures and lining figures Accounting *Figure, a synonym for number *Significant figures in a decimal number Science *Figure of the Earth, the size and shape of the Earth in geodesy Sports *Figure (horse), a sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mediator (coactivator)
Mediator is a multiprotein complex that functions as a transcriptional coactivator in all eukaryotes. It was discovered in 1990 in the lab of Roger D. Kornberg, recipient of the 2006 Nobel Prize in Chemistry. Mediator complexes interact with transcription factors and RNA polymerase II. The main function of mediator complexes is to transmit signals from the transcription factors to the polymerase. Mediator complexes are variable at the evolutionary, compositional and conformational levels. The first image shows only one "snapshot" of what a particular mediator complex might be composed of, but it certainly does not accurately depict the conformation of the complex ''in vivo''. During evolution, mediator has become more complex. The yeast ''Saccharomyces cerevisiae'' (a simple eukaryote) is thought to have up to 21 subunits in the core mediator (exclusive of the CDK module), while mammals have up to 26. Individual subunits can be absent or replaced by other subunits under differen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selective Factor 1
Selective factor 1 (also known as SL1) is a transcription factor that binds to the promoter of genes and recruits a preinitiation complex to which RNA polymerase I will bind to and begin the transcription of ribosomal RNA (rRNA). Discovery SL1 was discovered by Robert Tjian and his colleagues in 1985 when they separated a HeLa cell extract into two functional fractions. One factor has RNA polymerase I activity, but no ability to initiate accurate transcription of a human rRNA template. This transcription factor, SL1, showed species specificity. That is, it could distinguish between the human and mouse rRNA promoter, and added increasing amount of human template at the expense of the mice template. Tijian and coworkers went on to show that by footprinting a partially purified polymerase 1 preparation could bind to the human rRNA promoter. In particular it causes a footprint over a region of the UCE called ''A site''. This binding is not due to polymerase I itself but to a transc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UBTF
Nucleolar transcription factor 1 is a protein that in humans is encoded by the ''UBTF'' gene. Function Upstream binding factor (UBF) is a transcription factor required for expression of the 18S, 5.8S, and 28S ribosomal RNAs, along with SL1 (a complex of TBP (MIM 600075) and three TBP-associated factors or 'TAFs'). Two UBF polypeptides, of 94 and 97 kD, exist in the human (Bell et al., 1988). UBF is a nucleolar phosphoprotein with both DNA binding and transactivation domains. Sequence-specific DNA binding to the core and upstream control elements of the human rRNA promoter is mediated through several HMG boxes (Jantzen et al., 1990). upplied by OMIMref name="entrez" /> Interactions UBTF has been shown to interact with: * CSNK2A1, * RB1, * TAF1C, and * TAF1 Transcription initiation factor TFIID subunit 1, also known as transcription initiation factor TFIID 250 kDa subunit (TAFII-250) or TBP-associated factor 250 kDa (p250), is a protein that in humans is encoded by the ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeal Transcription Factor B
Archaeal transcription factor B (ATFB or TFB) is a protein family of extrinsic transcription factors that guide the initiation of RNA transcription in organisms that fall under the domain of Archaea. It is homologous to eukaryotic TFIIB and, more distantly, to bacterial sigma factor. Like these proteins, it is involved in forming transcription preinitiation complexes. Its structure includes several conserved motifs which interact with DNA and other transcription factors, notably the single type of RNA polymerase that performs transcription in Archaea. History In bacteria and eukaryotes, proteins TFIIB and sigma factor are involved in the initiation of transcription, where they facilitate preinitiation complex formation and specific RNA Polymerase-DNA binding. The archaeal counterpart to these two proteins is TFB, which was first identified in the species '' Pyrococcus woesei'' in 1992. Since then, research has found that archaeal species must contain at least one copy of TFB to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Polymerase II Holoenzyme
RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II that is recruited to the promoters of protein-coding genes in living cells. It consists of RNA polymerase II, a subset of general transcription factors, and regulatory proteins known as . RNA polymerase II RNA polymerase II (also called RNAP II and Pol II) is an enzyme found in eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. In humans, RNAP II consists of seventeen protein molecules (gene products encoded by POLR2A-L, where the proteins synthesized from ''POLR2C'', ''POLR2E'', and ''POLR2F'' form homodimers). General transcription factors General transcription factors (GTFs) or basal transcription factors are protein transcription factors that have been shown to be important in the transcription of class II genes to mRNA templates. Many of them are involved in the formation of a preinitiation complex, which, together with RNA polymerase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription Bubble
A transcription bubble is a molecular structure formed during DNA transcription when a limited portion of the DNA double helix is unwound. The size of a transcription bubble ranges from 12-14 base pairs. A transcription bubble is formed when the RNA polymerase enzyme binds to a promoter and causes two DNA strands to detach. It presents a region of unpaired DNA, where a short stretch of nucleotides are exposed on each strand of the double helix. RNA polymerase The bacterial RNA polymerase, a leading enzyme involved in formation of a transcription bubble, uses DNA template to guide RNA synthesis. It is present in two main forms: as a core enzyme, when it is inactive, and as a holoenzyme , when it is activated. A sigma (σ) factor is a subunit that assists the process of transcription and it stabilizes the transcription bubble when it binds to unpaired bases. These two components, RNA polymerase and sigma factor, when paired together, build RNA polymerase holoenzyme which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Supercoil
DNA supercoiling refers to the amount of twist in a particular DNA strand, which determines the amount of strain on it. A given strand may be "positively supercoiled" or "negatively supercoiled" (more or less tightly wound). The amount of a strand’s supercoiling affects a number of biological processes, such as compacting DNA and regulating access to the genetic code (which strongly affects DNA metabolism and possibly gene expression). Certain enzymes, such as topoisomerases, change the amount of DNA supercoiling to facilitate functions such as DNA replication and transcription. The amount of supercoiling in a given strand is described by a mathematical formula that compares it to a reference state known as "relaxed B-form" DNA. Overview In a "relaxed" double-helical segment of B-DNA, the two strands twist around the helical axis once every 10.4–10.5 base pairs of sequence. Adding or subtracting twists, as some enzymes do, imposes strain. If a DNA segment under twist s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicase
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two hybridized nucleic acid strands (hence '' helic- + -ase''), using energy from ATP hydrolysis. There are many helicases, representing the great variety of processes in which strand separation must be catalyzed. Approximately 1% of eukaryotic genes code for helicases. The human genome codes for 95 non-redundant helicases: 64 RNA helicases and 31 DNA helicases. Many cellular processes, such as DNA replication, transcription, translation, recombination, DNA repair, and ribosome biogenesis involve the separation of nucleic acid strands that necessitates the use of helicases. Some specialized helicases are also involved in sensing of viral nucleic acids during infection and fulfill a immunological function. Function Helicases are o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ATPase
ATPases (, Adenosine 5'-TriPhosphatase, adenylpyrophosphatase, ATP monophosphatase, triphosphatase, SV40 T-antigen, ATP hydrolase, complex V (mitochondrial electron transport), (Ca2+ + Mg2+)-ATPase, HCO3−-ATPase, adenosine triphosphatase) are a class of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion or the inverse reaction. This dephosphorylation reaction releases energy, which the enzyme (in most cases) harnesses to drive other chemical reactions that would not otherwise occur. This process is widely used in all known forms of life. Some such enzymes are integral membrane proteins (anchored within biological membranes), and move solutes across the membrane, typically against their concentration gradient. These are called transmembrane ATPases. Functions Transmembrane ATPases import metabolites necessary for cell metabolism and export toxins, wastes, and solutes that can hinder cellular processes. An important example is the sodium-potass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TBPL1
TATA box-binding protein-like protein 1 is a protein that in humans is encoded by the ''TBPL1'' gene. Function Initiation of transcription by RNA polymerase II requires the activities of more than 70 polypeptides. The protein that coordinates these activities is transcription factor IID (TFIID), which binds to the core promoter to position the polymerase properly, serves as the scaffold for assembly of the remainder of the transcription complex, and acts as a channel for regulatory signals. TFIID is composed of the TATA-binding protein (TBP) and a group of evolutionarily conserved proteins known as TBP-associated factors or TAFs. TAFs may participate in basal transcription, serve as coactivators, function in promoter recognition or modify general transcription factors (GTFs) to facilitate complex assembly and transcription initiation. This gene encodes a protein that serves the same function as TBP and substitutes for TBP at some promoters that are not recognized by TFIID. It is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
