| transcription factor | <molecular biology> Protein required for recognition by RNA polymerases of specific stimulatory sequences in eukaryotic genes. Several are known that activate transcription by RNA polymerase II when bound to upstream promoters. Transcription of the 5S RNA gene in Xenopus by RNA polymerase III is dependent on a 40 kD protein TFIIIA that binds to a regulatory site in the centre of the gene and was the first protein found to exhibit the metal binding domains known as zinc fingers. (17 Mar 1998) |
|---|---|
| transcription factor ap-1 | A multiprotein complex composed of the products of c-jun and c-fos proto-oncogenes. These proteins must dimerise in order to bind to the ap-1 recognition site, also known as the tpa-responsive element (tre). Ap-1 controls both basal and inducible transcription of several genes. (12 Dec 1998) |
| transcription factor, sp1 | Promoter-specific RNA polymerase II transcription factor that binds to the gc box, one of the upstream promoter elements (upe) in mammalian cells. The binding of sp1 is necessary to initiate transcription in the promoters of a variety of cellular and viral genes including c-ha-ras and HIV. (12 Dec 1998) |
| transcription factors | Endogenous substances, usually proteins, which are effective in the initiation, stimulation, or termination of the genetic transcription process. (12 Dec 1998) |
| transcription factors, tfii | The so-called general transcription factors that bind to RNA polymerase II and that are required to initiate transcription. They include tfiia, tfiib, tfiid, tfiie, tfiif, tfiih, tfii-I, and tfiij. In vivo they apparently bind in an ordered multi-step process and/or may form a large preinitiation complex called RNA polymerase II holoenzyme. (12 Dec 1998) |
| transcription factors, tfiii | Factors that bind to RNA polymerase III and aid in transcription. They include the assembly factors tfiiia and tfiiic and the initiation factor tfiiib. All combine to form a preinitiation complex at the promotor that directs the binding of RNA polymerase III. (12 Dec 1998) |
| transcription unit | <molecular biology> A region of DNA that is transcribed to produce a single primary RNA transcript, i.e. A newly synthesised RNA molecule that has not been processed. Transcription units can be mapped by kinetic studies of RNA synthesis and in some instances directly visualised by electron microscopy. (17 Mar 1998) |
| transcription, genetic | The transfer of genetic information from DNA to messenger RNA by DNA-directed RNA polymerase. It includes reverse transcription and transcription of early and late genes expressed early in an organism's life cycle or during later development. (12 Dec 1998) |
| transcriptional control | <molecular biology> Control of gene expression by controlling the number of RNA transcripts of a region of DNA. A major regulatory mechanism for differential control of protein synthesis in both pro and eukaryotic cells. (18 Nov 1997) |
| transcriptional silencing | <molecular biology> Mechanism of transcriptional control where DNA is bundled into heterochromatin in order to make it permanently inaccessible for future transcription. Effectively, this allows for memory in the determination of cell fate in developing organisms. In Drosophila, homeotic genes are silenced by members of the Polycomb group of genes. (17 Mar 1998) |
| transcultural nursing | A nursing specialty created to answer the need for developing a global perspective in the practice of nursing in a world of interdependent nations and people. The focus of this nursing discipline is on the integration of international and transcultural content into the training. Courses include study in the area of cultural differences, nursing in other countries, and international health issues and organizations, as an example. (12 Dec 1998) |
| transcutaneous | <pharmacology> Entering through the dermis or skin, as in administration of a drug applied to the skin in ointment or patch form. (17 Mar 1998) |
| transcutaneous electric nerve stimulation | Electrical stimulation of nerves and/or muscles to relieve pain; it is used less frequently to produce anaesthesia. The optimal placements of electrodes or "trigger points" may correspond with acupuncture analgesia points. Tens is sometimes referred to as acupuncture-like when using a low frequency stimulus. (12 Dec 1998) |
| transcytosis | <cell biology> Process of transport of material across an epithelium by uptake on one face into a coated vesicle, which may then be sorted through the trans Golgi network and transported to the opposite face in another set of vesicles. (17 Mar 1998) |
| transcytotic vesicle | <cell biology> Membrane bounded vesicle that shuttles fluid from one side of the endothelium to the other. There is some controversy as to whether or not they form pores. (17 Mar 1998) |