ZOOHCC - 501: Molecular Biology (Theory)

Unit 3: Transcription and Regulatory RNAs


















    Transcription factors




    Transcription factors are proteins that regulate the transcription of
    genes. That is, copying into RNA on the way to protein.




    Explanation



    Transcription factor, a molecule that controls the activity of a gene by
    determining whether the gene's DNA (deoxyribonucleic acid) is transcribed
    into RNA (ribonucleic acid). The enzyme RNA polymerase catalyzes the
    chemical reaction that synthesizes RNA using the DNA of a gene as a
    template. Transcription factors control when, where, and how efficiently RNA
    polymerase functions.



    Transcription factors are essential not only for normal development of an
    organism, but also for routine cellular function and disease response.
    Transcription factors are a diverse family of proteins that generally
    function in multisubunit protein complexes. They can either bind directly to
    specific 'promoter' regions of DNA located upstream of the coding regions of
    genes, or they can bind directly to RNA polymerase molecules. Transcription
    factors can activate or repress the transcription of genes. This is
    generally a key determinant of whether a gene is functioning at a given
    time.



    Basic or general transcription factors are required for the function of RNA
    polymerase at eukaryotic transcription sites. They are considered to be the
    most basic group of proteins required to activate gene transcription, among
    which many proteins such as TFIIA (transcription factor II A) and TFIIB
    (transcription factor II B) are It contains. Significant progress has been
    made in defining the role played by each protein that makes up the basal
    transcription factor complex. During the development of multicellular
    organisms, transcription factors play a role in determining the fate of
    individual cells. For example, homeotic genes control patterns of body
    formation, and these genes encode transcription factors that instruct cells
    to form different parts of the body. Homeotic proteins activate one gene and
    repress another, producing complementary effects necessary for the orderly
    development of the organism. If one of the homeotic transcription factors
    mutates, the organism will not develop properly. For example, in Drosophila,
    mutations in certain homeotic genes alter transcription so that legs grow on
    the head instead of the antennae. This is known as Antennapedia mutation.
    Transcription factors are a common way cells respond to extracellular
    information. B. Environmental stimuli and signals from other cells.
    Transcription factors may play important roles in cancer by influencing the
    activity of genes involved in the cell cycle (or cell division cycle). In
    addition, transcription factors can be the products of oncogenes (genes that
    can cause cancer) or tumor suppressor genes (genes that suppress
    cancer).



    Transcription factors act in the nucleus, where genes are located, and
    nuclear transport (ie, import or export) of transcription factors can affect
    their activity. Another important general mechanism controlling the activity
    of transcription factors is post-translational modifications such as
    phosphorylation. Finally, these protein complexes not only regulate the
    transcription of genes and other transcription factors, but can also
    regulate genes responsible for their own transcription, resulting in complex
    feedback control mechanisms.



    transcription factors mechanism



    Activator: Some transcription factors activate transcription. For example, they can
    help common transcription factors and RNA polymerases bind to promoters,
    as shown in the diagram below.



    Repressor: Other transcription factors repress transcription. This suppression
    works in different ways. For example, repressors interfere with basic
    transcription factors or RNA polymerases, preventing them from binding
    to promoters and initiating transcription.



    Binding site: Binding sites for transcription factors are often located near the
    promoters of genes. However, they can also occur at other sites in the
    DNA, sometimes very far from the promoter, and affect gene transcription.
    The parts of the activator protein: the DNA-binding domain (which binds to
    the recognition site on DNA) and the activation domain, the activator's
    "shop end" that actually promotes transcription. B. By promoting the
    formation of transcription initiation complexes. The parts of the
    activator protein: the DNA-binding domain (which binds to the recognition
    site on DNA) and the activation domain, the activator's "shop end" that
    actually promotes transcription. B. By promoting the formation of
    transcription initiation complexes. The flexibility of DNA allows
    transcription factors at distant binding sites to do their job. DNA
    meanders like cooked spaghetti, bringing distant binding sites and
    transcription factors closer to a common transcription factor, or
    'mediator' protein.