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General transcription factors bind to the promoter. When a transcription factor is activated by a signal (here indicated as phosphorylation shown by a small red star on a transcription factor on the enhancer) the enhancer is activated and can now activate its target promoter. The active enhancer is transcribed on each strand of DNA in opposite ...
Other transcription factors differentially regulate the expression of various genes by binding to enhancer regions of DNA adjacent to regulated genes. These transcription factors are critical to making sure that genes are expressed in the right cell at the right time and in the right amount, depending on the changing requirements of the organism.
Factors influencing viral tissue tropism include: The presence of cellular receptors permitting viral entry. Availability of transcription factors involved in viral replication. The molecular nature of the viral tropogen or virus surface, such as the glycoprotein, which interacts with the corresponding cell receptor.
Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome and packaging these copies, the virus continues infecting new hosts. Replication between viruses is ...
U3 and U5 has been further subdivided according to transcription factor sites and their impact on LTR activity and viral gene expression. The multi-step process of reverse transcription results in the placement of two identical LTRs, each consisting of a U3, R, and U5 region, at either end of the proviral DNA.
Viral genes are expressed through the use of the host cell's replication machinery; therefore, many viral genes have promoters that support binding of many transcription factors found naturally in the host cells. These transcription factors along with the virus' own proteins can repress or activate genes from both the virus and the host cell's ...
Interferon regulatory factors (IRF) are proteins which regulate transcription of interferons (see regulation of gene expression). [1] Interferon regulatory factors contain a conserved N-terminal region of about 120 amino acids, which folds into a structure that binds specifically to the IRF-element (IRF-E) motifs, which is located upstream of the interferon genes. [2]
Various factors affect the ability of a pathogen to infect a particular cell, including: the structure of the cell's surface receptors; the availability of transcription factors that can identify pathogenic DNA or RNA; the ability of the cells and tissue to support viral or bacterial replication; and the presence of physical or chemical ...