Corps de l’article
Expression de l’information génétique
Au sein d’un organisme, une information génétique identique conduit à l’élaboration de phénotypes cellulaires différents, ce qu’expliquent l’activation et/ou la répression sélectives d’un répertoire de gènes. Ces événements moléculaires permettent également la réponse appropriée de la cellule à une variation locale des concentrations en hormones. La transcription requiert la présence de l’ARN polymérase II (Pol II), recrutée au niveau du promoteur du gène sous l’influence de la liaison d’un ou de plusieurs facteurs de transcription dits enhancer sur des séquences cis précises. Cet enhancer va provoquer la mise en place du complexe de pré-initiation (CPI) au niveau du site d’initiation de la transcription. Le CPI inclut la Pol II inactive ainsi que les six complexes TFIIA, B, C, D, E et F [1]. D’autres complexes protéiques composés de plusieurs sous-unités, les TRAP/DRIP/Mediator (TRAP pour thyroid receptor-associated protein complex, DRIP pour vitamin D receptor interacting proteins),∈établissent un pont entre le CPI et l’activateur et permettent la transition entre le CPI et un complexe Pol II compétent pour la transcription. Cette transition est due à la phosphorylation de la sous-unité Rbp1 (ou extension carboxy-terminale) de la Pol II qui permet un échange des protéines de type Mediator pour des protéines spécifiques (de type Elongator) de la Pol II active.
Chromatine et dynamique d’activation de la transcription d’un gène
Au sein de la chromatine, l’ADN est compacté par les histones sous forme de nucléosomes. L’initiation de la transcription d’un gène se déroule donc in vivo dans un contexte très restrictif, car cette structure compacte est physiquement peu propice à la liaison des complexes protéiques de haut poids moléculaire formant le CPI. Au niveau du promoteur, la plasticité de la chromatine requise pour l’initiation de la transcription est assurée par le recrutement et l’assemblage de complexes protéiques spécifiques [2]. Ces événements impliquent soit des protéines de type SWI/SNF qui altèrent l’organisation spatiale des nucléosomes en présence d’ATP, soit des protéines qui, en modifiant les lysines et les arginines des histones tails par acétylation (activité HAT, histone acétyltransférase) ou méthylation (HMT, histone méthyltransférase), vont affaiblir les liaisons physiques entre les histones et l’ADN [3]. Il y a déjà maintenant près de 20 ans, s’est posé la question de la cinétique de ces événements : les complexes recrutés au niveau d’un promoteur sont-ils déjà préformés ou bien s’assemblent-ils sur le promoteur, et dans quel ordre ?
Le modèle des signalisations oestrogéniques
Les oestrogènes, comme le 17β-oestradiol (E2), sont des hormones lipophiles qui contrôlent un grand nombre de processus physiologiques via la modulation de l’expression de gènes cibles. Cela s’opère par l’intermédiaire de récepteurs nucléaires spécifiques, les récepteurs des oestrogènes (ER), qui se fixent sur des séquences spécifiques (ERE pour estrogen responsive element) situées dans le promoteur du gène sélectionné. Ces facteurs de transcription majoritairement activateurs interagissent avec certains des composants du CPI, SWI/SNF, des HAT (comme SRC1 et CBP/p300) et des HMT (comme CARM1 et PRMT1), ainsi qu’avec les complexes de type TRAP/Mediator [4]. En utilisant des techniques d’immunoprécipitation de complexes chromatiniens (ChIP) et une étude cinétique des remodelages de la chromatine au niveau du promoteur du gène pS2 contrôlé par les oestrogènes in vivo, nous avons récemment défini plusieurs points importants et novateurs pour la compréhension des mécanismes d’initiation de la transcription [5].
Activation de la transcription: un processus combinatoire, cyclique et séquentiel
La première conclusion de ces expériences est que l’association des complexes régulateurs avec la chromatine est cyclique, et se produit toutes les 40 à 45 minutes sur notre promoteur modèle. L’activation de la Pol II se fait en cinq à dix minutes (Figure 1A). Lors de ces cycles, la structure chromatinienne du promoteur pS2 alterne entre des états permissifs et non permissifs pour la transcription. Ces transitions, créées par des fluctuations régulières du positionnement des nucléosomes et des niveaux d’acétylation et de méthylation des histones, sont sous l’influence de recrutements coordonnés par l’ER d’enzymes de type SWI/SNF, HAT et HMT. De plus, des complexes protéiques habituellement considérés comme répresseurs de la transcription (par exemple les HDAC, histone désacétylase), sont impliqués dans la genèse de ces cycles. Enfin, la dégradation de l’ER par le protéasome définit un point d’arrêt à la stimulation de la transcription du gène pS2(Figure 1B).
A. Expérience de ChIP (immunoprécipitation de la chromatine), mesurant in vivo la permissivité du promoteur pS2 à la liaison du récepteur de l’oestrogène (ER) et au recrutement de la polymérase II (Pol II). Ces mesures mettent en évidence deux types de cycles ; seul le second type permet un recrutement cyclique de la Pol II toutes les 45 minutes. B. Illustration des séquences de recrutement de divers facteurs de transcription dans les deux cycles, et de leur conséquence au niveau de l’organisation chromatinienne du promoteur. Le premier cycle est appelé « initiateur », car il prépare le promoteur à répondre ensuite au niveau transcriptionnel. Dans les deux cas, la dégradation de l’ER par le protéasome termine le cycle. C. Les astérisques rouges indiquent les points où nous avons observé un recrutement combinatoire, c’est-à-dire un recrutement alternatif de protéines ayant la même activité, comme par exemple CARM1 et PRMT1.
-> Voir la liste des figures
La seconde observation révèle que plusieurs combinaisons de protéines différentes peuvent assurer chacune des étapes de cette séquence complexe d’événements enzymatiques, reflétant une redondance fonctionnelle entre les protéines recrutées in vivo(Figure 1C). On peut donc parler de recrutements stochastiques : pour un promoteur et une cellule données, une parmi plusieurs protéines ayant la même activité va avoir une certaine probabilité de se lier sur le promoteur. Une préférence de recrutement, certainement due à une différence d’affinité entre les protéines, a été montrée dans le cas de récepteurs d’autres hormones stéroïdes [6].
Existence d’un «synchronisateur» allostérique
La transcription d’un gène serait donc un processus cyclique au cours duquel les protéines régulatrices recrutées s’associeraient et se dissocieraient continuellement. On doit donc postuler l’existence d’un mécanisme de contrôle de ces cycles qui synchronise l’accessibilité du promoteur pour tel ou tel complexe protéique et qui orchestre la progression des cycles à travers une séquence d’événements requis pour une activation transcriptionnelle. Ce « synchronisateur » serait créé par des processus allostériques mettant en jeu à la fois des événements ayant lieu au niveau de la structure même du promoteur, et des activités enzymatiques apportées par tel ou tel facteur de transcription. Par exemple, illustrant le concept du « code histone » [7], un changement dans le statut d’acétylation et de méthylation des histones peut être un des éléments essentiels de cette signalétique, permettant à la cellule de savoir à quelle étape particulière du cycle se situe le promoteur. De plus, certaines protéines sont recrutées si et seulement si une histone du promoteur est acétylée ou méthylée [8]. Les changements conformationnels produits au sein de deux partenaires interagissant physiquement représentent en eux-mêmes un signal pouvant également marquer l’état de progression des complexes présents sur le promoteur dans le cycle d’activation de la transcription.
Un modèle général pour l’initiation de la transcription ?
La séquence de recrutement des protéines que nous avons décrite ne peut vraisemblablement pas être extrapolée au fonctionnement de tous les promoteurs, car d’autres enchaînements ont été observés, notamment au niveau du gène IFNβ [9]. En revanche, nous proposons, et d’autres auteurs partagent cette vision [10], que les principes qui se dégagent de nos résultats servent pour établir un modèle général. Une initiation de la transcription résulte : (1) du recrutement séquentiel et stochastique de protéines redondantes ; et (2) de processus cycliques assurés par un « synchronisateur » qui contrôle ces recrutements et les modifications structurales du promoteur. Cela reste cependant à confirmer dans d’autres systèmes modèles. L’intérêt primordial du caractère cyclique de ces événements serait de permettre à la cellule de pouvoir ajuster la transcription d’un gène à une situation précise, telle qu’on peut la rencontrer lors des variations du taux d’hormones circulantes auxquelles elle doit s’adapter.
Parties annexes
Références
- 1.Berk AJ. Activation of RNA polymerase II transcription. Curr Opin Cell Biol 1999 ; 11 : 330-5.
- 2.Dillon N, Festenstein R. Unraveling heterochromatin : competition between positive and negative factors regulates accessibility. Trends Genet 2002 ; 18 : 252-8.
- 3.Berger SL. Histone modifications in transcriptional regulation. Curr Opin Genet Dev 2002 ; 12 : 142-8.
- 4.Klinge CM. Estrogen receptor interaction with co-activators and co-repressors. Steroids 2000 ; 65 : 227-51.(Video) Au-delà des gènes, régulation épigénétique du cerveau à travers les générations
- 5.Metivier R, Penot G, Hubner MR, etal. Estrogen receptor-alpha directs ordered, cyclical, and combinatorial recruitment of cofactors on a natural target promoter. Cell 2003 ; 115: 751-63.
- 6.Li X, Wong J, Tsai SY, et al. Progesterone and glucocorticoid receptors recruit distinct coactivator complexes and promote distinct patterns of chromatin modification. Mol Cell Biol 2003 ; 23 : 3763-73.
- 7.Jenuwein T, Allis CD. Translating the histone code. Science 2001 ; 293 : 1074-9.(Video) MOOC côté cours : Les différents types de récepteurs cellulaires
- 8.Hassan AH, Neely KE, Workman JL. Histone acetyltransferase complexes stabilize swi/snf binding to promoter nucleosomes. Cell 2001 ; 104 : 817-27.
- 9.Agalioti T, Chen G, Thanos D. Deciphering the transcriptional histone acetylation code for a human gene. Cell 2002 ; 111 : 381-92.
- 10.Vermeulen W, Houtsmuller AB. The transcription cycle in vivo. A blind watchmaker at work. Mol Cell 2002 ; 10 : 1264-6.
Liste des figures
A. Expérience de ChIP (immunoprécipitation de la chromatine), mesurant in vivo la permissivité du promoteur pS2 à la liaison du récepteur de l’oestrogène (ER) et au recrutement de la polymérase II (Pol II). Ces mesures mettent en évidence deux types de cycles ; seul le second type permet un recrutement cyclique de la Pol II toutes les 45 minutes. B. Illustration des séquences de recrutement de divers facteurs de transcription dans les deux cycles, et de leur conséquence au niveau de l’organisation chromatinienne du promoteur. Le premier cycle est appelé « initiateur », car il prépare le promoteur à répondre ensuite au niveau transcriptionnel. Dans les deux cas, la dégradation de l’ER par le protéasome termine le cycle. C. Les astérisques rouges indiquent les points où nous avons observé un recrutement combinatoire, c’est-à-dire un recrutement alternatif de protéines ayant la même activité, comme par exemple CARM1 et PRMT1.
FAQs
What is the activation of a gene that results in transcription? ›
Activation of a gene — transcription — is kicked off when proteins called transcription factors bind to two key bits of DNA, an enhancer and a promoter. These are far from each other, and no one knew how close they had to come for transcription to happen.
What is the function of an activator? ›Activators are considered to have positive control over gene expression, as they function to promote gene transcription and, in some cases, are required for the transcription of genes to occur. Most activators are DNA-binding proteins that bind to enhancers or promoter-proximal elements.
What is the transcription of the gene expression? ›Transcription is the first step in gene expression. It involves copying a gene's DNA sequence to make an RNA molecule. Transcription is performed by enzymes called RNA polymerases, which link nucleotides to form an RNA strand (using a DNA strand as a template).
What is gene expression quizlet? ›gene expression. the activation, or "turning on" of a gene that results in transcription and the production of mRNA. genome. the complete genetic material contained in an individual.
How long does gene transcription take? ›Similarly, an average bacterial gene is 1 kbp long and thus will take about a minute to transcribe, while introns cause the average mammalian gene to be 10 kbp long and thus will take about 10 min. Similar timescale differences occur in additional cellular processes, such as the turnover of metabolites.
What is gene activation and why is it important? ›The process of activation of a gene so that it is expressed at a particular time. This process is crucial in growth and development.
What is an example of an activator in transcription? ›One example of an activator is the protein CAP. In the presence of cAMP, CAP binds to the promoter and increases RNA polymerase activity. In the absence of cAMP, CAP does not bind to the promoter. Transcription occurs at a low rate.
What is the role and example of enzyme activator? ›These molecules are often involved in the allosteric regulation of enzymes in the control of metabolism. An example of an enzyme activator working in this way is fructose 2,6-bisphosphate, which activates phosphofructokinase 1 and increases the rate of glycolysis in response to the hormone glucagon.
What is a simple example of activator? ›The most well-known example of such type of activators is Ca-binding protein calmodulin (calcium-modulated protein) that is expressed in all eukaryotic cells. Calmodulin is a small protein containing 148 amino acids (16.7 kDa).
How can genes be turned on or off? ›The gene regulatory proteins allow the individual genes of an organism to be turned on or off specifically. Different selections of gene regulatory proteins are present in different cell types and thereby direct the patterns of gene expression that give each cell type its unique characteristics.
What enzyme is required for transcription? ›
Transcription is carried out by an enzyme called RNA polymerase and a number of accessory proteins called transcription factors.
How do you go from DNA to mRNA? ›During transcription, the DNA of a gene serves as a template for complementary base-pairing, and an enzyme called RNA polymerase II catalyzes the formation of a pre-mRNA molecule, which is then processed to form mature mRNA (Figure 1).
How is RNA different from DNA? ›Whereas DNA always occurs in cells as a double-stranded helix, RNA is single-stranded. RNA chains therefore fold up into a variety of shapes, just as a polypeptide chain folds up to form the final shape of a protein (Figure 6-6).
Why is gene expression important? ›Gene expression is important because a specific protein can be produced only when its gene is turned on. But it takes more than one step to get from gene to protein, and the process of building proteins is a key step in the gene expression pathway that can be altered in cancer.
What is the role of RNA polymerase in transcription? ›RNA polymerase (green) synthesizes RNA by following a strand of DNA. RNA polymerase is an enzyme that is responsible for copying a DNA sequence into an RNA sequence, duyring the process of transcription.
How hard is it to get into transcription? ›It requires patience and serious training. The job might involve transcribing recordings of legal, medical, and other topics. Becoming a transcriptionist requires having excellent typing skills and keen hearing. It requires accuracy and a commitment to producing a written document of high quality.
How accurate is transcription? ›Transcription accuracy rates give insight into the percentage of error a transcript can have per word count. For example, a transcription accuracy of 99% means there is a 1% chance of errors per every 1,500 words or about 15 errors. 99% accuracy = 1% chance of errors. Or, about 15 errors every 1,500 words.
How many times can DNA be transcribed? ›Answer and Explanation: A gene can be transcribed many times, whenever the protein product that the gene encodes is required by the cell. Transcription is the first step in gene expression whereby a gene within the DNA is used to make a complementary mRNA)molecule.
What happens if I tell gene to leave high on life? ›If the player tells Gene to leave, he threatens to take his bounty hunting equipment with him before affirming that it is clear he is still needed even if he isn't wanted. Either way, Gene stays. The only change is the dialogue that will come from the decision.
What are three benefits of gene sequencing? ›- •Allows doctors to closely analyze a patient's genes for mutations and health indicators.
- •Can detect intellectual disabilities and developmental delays.
- •WGS is currently available at Yale for patients in the NICU and PICU.
- •Involves Genetics.
Which hormones use direct gene activation? ›
Receptors that can directly influence gene expression are termed nuclear receptors. Located within the cytosol or nucleus, nuclear receptors are the target of steroid and thyroid hormones that are able to pass through the cell membrane.
Do you need an activator for transcription? ›Transcriptional activators are required to turn on the expression of genes in a eukaryotic cell. Activators bound to the enhancer can facilitate either the recruitment of RNA polymerase II to the promoter or its elongation.
What prevents transcription? ›An inactive repressor protein (blue) can become activated by another molecule (red circle). This active repressor can bind to a region near the promoter called an operator (yellow) and thus interfere with RNA polymerase binding to the promoter, effectively preventing transcription.
What is the difference between an enhancer and an activator? ›An enhancer is a DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements. Activators bound to the distal control elements interact with mediator proteins and transcription factors.
What are three examples of how enzymes are used in industry? ›Enzymes are used in industrial processes, such as baking, brewing, detergents, fermented products, pharmaceuticals, textiles, leather processing.
What are two examples of essential elements that act as activators for enzymes? ›Iron, manganese, magnesium, zinc, molybdenum, etc., are act as enzyme activator. For example, Mo activate enzyme and helps in fixation. 1. In photosynthetic carbon fixation, magnesium ion (Mg2) is an activator for both ribulose bisphosphate carboxylase / oxygenase and phosphoenolpyruvate carboxylase enzymes.
What are two types of activators? ›What are the two types of activators? Cofactors and Coenzymes.
What is an activator drug? ›An agonist or activator, is a drug or chemical that binds to and activates a protein, such as receptor or enzyme.
What is an activator example biology? ›What are some examples of activators in biology? Examples of activators include the cAMP response element-binding protein (CREB), the glucocorticoid receptor (GR), the nuclear factor kappa B (NF-κB), and the estrogen receptor (ER).
Which element is an activator? ›Solution: Magnesium is an activator for both ribulose bisphosphate carboxylase oxygenase and phosphoenolpyruvate carboxylase.
Does trauma change your DNA? ›
Here's how: Trauma can leave a chemical mark on a person's genes, which can then be passed down to future generations. This mark doesn't cause a genetic mutation, but it does alter the mechanism by which the gene is expressed. This alteration is not genetic, but epigenetic.
How can I change my genes naturally? ›Being well rested, avoiding stress, finding happiness throughout the day, and healthy diet and exercise all contribute to our well-being on a much deeper level. Surprisingly, recent and ongoing research suggests that positive behavioral and lifestyle changes can actually affect you on a genetic level.
What does it mean if a gene is turned off? ›When a gene is turned off, it no longer provides the directions for making proteins. This means that the proteins needed to fulfill a particular job -- say, tolerate lactase -- aren't produced.
What are the 3 enzymes in transcription? ›DNA transcription uses three polymerase enzymes – RNA polymerase I, RNA polymerase II, and RNA polymerase III. Although the structures of all three polymerase enzymes are homologous, they perform different functions. RNA polymerase I plays a role in the transcription of ribosomal RNA.
What does mRNA do? ›What is mRNA? mRNA—or messenger RNA—is a molecule that contains the instructions or recipe that directs the cells to make a protein using its natural machinery. To enter cells smoothly, mRNA travels within a protective bubble called a Lipid Nanoparticle.
What is reverse transcription in viruses? ›(ree-VERS tran-SKRIP-shun) In biology, the process in cells by which an enzyme makes a copy of DNA from RNA. The enzyme that makes the DNA copy is called reverse transcriptase and is found in retroviruses, such as the human immunodeficiency virus (HIV).
What happens when A gene is repressed? ›Gene repression is the switching off of individual genes whose products are needed to maintain the function of the cell such as the production of vital enzymes or cofactors. This is especially important if the products of such genes are not long-lived and deteriorate, or are metabolized.
Where does the mRNA go now? ›The mRNA is then pulled through the ribosome; as its codons encounter the ribosome's active site, the mRNA nucleotide sequence is translated into an amino acid sequence using the tRNAs as adaptors to add each amino acid in the correct sequence to the end of the growing polypeptide chain.
What is mRNA made in? ›mRNA is synthesized in the nucleus using the nucleotide sequence of DNA as a template. This process requires nucleotide triphosphates as substrates and is catalyzed by the enzyme RNA polymerase II. The process of making mRNA from DNA is called transcription, and it occurs in the nucleus.
Which is better DNA or RNA? ›Due to its deoxyribose sugar, which contains one less oxygen-containing hydroxyl group, DNA is a more stable molecule than RNA, which is useful for a molecule which has the task of keeping genetic information safe.
Where is RNA located? ›
Ribosomal RNA (rRNA) is the most common form of RNA found in cells – it makes up around 50% of the structure of the ribosomes. It is produced in the nucleus, before moving out into the cytoplasm to bind with proteins and form a ribosome. Transfer RNA (tRNA) is found in the cytoplasm and has a complex shape.
Where is DNA located in the body? ›Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA). Mitochondria are structures within cells that convert the energy from food into a form that cells can use.
What controls gene expression? ›Gene expression is primarily controlled at the level of transcription, largely as a result of binding of proteins to specific sites on DNA.
What triggers gene expression? ›Gene expression is the process by which the information encoded in a gene is turned into a function. This mostly occurs via the transcription of RNA molecules that code for proteins or non-coding RNA molecules that serve other functions.
How do you activate genes? ›Activation of a gene — transcription — is kicked off when proteins called transcription factors bind to two key bits of DNA, an enhancer and a promoter. These are far from each other, and no one knew how close they had to come for transcription to happen.
What is the role of the DNA polymerase? ›The primary role of DNA polymerases is to accurately and efficiently replicate the genome in order to ensure the maintenance of the genetic information and its faithful transmission through generations.
What are the 4 functions of RNA polymerase? ›In eukaryotes, there are many types of RNA Pol enzymes that have different functions: RNA Pol I: It synthesises pre-rRNA subunits that form the ribosomes. RNA Pol II: It synthesises precursors of microRNA, snRNA and mRNA. RNA Pol III: It synthesises tRNA, other precursors of rRNA and some small RNAs.
What does DNA translation produce? ›In biology, the process by which a cell makes proteins using the genetic information carried in messenger RNA (mRNA). The mRNA is made by copying DNA, and the information it carries tells the cell how to link amino acids together to form proteins.
What is the activation of a gene that results in transcription and the production of mRNA? ›The correct answer is: Gene expression.
What causes transcription activation? ›Transcription is initiated when one TF binds to one of these promoter sequences, initiating a series of interactions between multiple proteins (activators, regulators, and repressors) at the same site, or other promoter, regulator, and enhancer sequences.
What is the activation of transcription initiation? ›
Transcription initiation is the phase during which the first nucleotides in the RNA chain are synthesized. It is a multistep process that starts when the RNAP holoenzyme binds to the DNA template and ends when the core polymerase escapes from the promoter after the synthesis of approximately the first nine nucleotides.
How is transcription activated? ›The activity of inducible transcription factors can be regulated by several mechanisms, such as phosphorylation or dephosphorylation, binding of activating or inhibitory factors, or de novo synthesis. Transcription factors play critical roles in the development and function of the immune system [reviewed in 6–9].
What are the main functions of transcription factors that activate RNA transcription? ›Transcription factors are vital molecules in the control of gene expression, directly controling when, where and the degree to which genes are expressed. They bind to specific sequences of DNA and control the transcription of DNA into mRNA.
What happens during gene activation? ›Gene activation by the GR proceeds by a widely accepted mechanism in which hormone diffuses across the cell membrane into the cytoplasm to where the receptor is held in an inactive complex by heat-shock proteins.
What happens to DNA when it is transcribed into mRNA? ›During transcription, the enzyme RNA polymerase (green) uses DNA as a template to produce a pre-mRNA transcript (pink). The pre-mRNA is processed to form a mature mRNA molecule that can be translated to build the protein molecule (polypeptide) encoded by the original gene.
What diseases are associated with transcription? ›The transcription factor controls genes involved in inflammation, and is chronically active in inflammatory diseases such as inflammatory bowel disease, arthritis, sepsis, gastritis, asthma and atherosclerosis.
What does it mean when we say a gene is turned off? ›These sequences hold directions for making the proteins that will carry out a cell's particular function. This is how one cell might end up being important to your kidneys, while another cell makes bone. When a gene is turned off, it no longer provides the directions for making proteins.
What triggers cells to stop transcription? ›a | Transcription termination at protein-coding genes is triggered by cleavage and polyadenylation specificity factor (CPSF), cleavage stimulatory factor (CstF), cleavage factor I (CFI) and CFII, which contain homologues of components of the yeast cleavage and polyadenylation factor (CPF)–CF complex.
What happens to the DNA after transcription? ›Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). DNA safely and stably stores genetic material in the nuclei of cells as a reference, or template.
What are the 3 classes of proteins involved in activation of transcription initiation? ›Transcription of eukaryotic nuclear genes requires three different RNA polymerases: RNA polymerase I, RNA polymerase II and RNA polymerase III.
What enzyme activates transcription? ›
The enzymes that perform transcription are called RNA polymerases. Like the DNA polymerase that catalyzes DNA replication (discussed in Chapter 5), RNA polymerases catalyze the formation of the phosphodiester bonds that link the nucleotides together to form a linear chain.
What controls transcription? ›As in bacteria, transcription in eukaryotic cells is controlled by proteins that bind to specific regulatory sequences and modulate the activity of RNA polymerase.
Why is transcription important? ›– transcription ensures the reliable transfer of information capable of changing lives, and 100% accuracy is essential. Any issues with transcription in legal or healthcare settings, for example, can have a significant impact on the lives of individuals or groups of people.