Proteins in a family of transcription factors (DNA binding molecules that activa

Question

Proteins in a family of transcription factors (DNA binding molecules that activate transcription) have 2 distinct domains: activation domain (AD) and DNA binding domain (DBD). These are not steroid hormone receptors since they do not require hormone binding to do their job. While studying a transcription factor (XP) you discover that if you break these two domains apart and attach them to two separate molecules (Y and Z) the transcription factor would still function as long as Y and Z bind to each other.

Which of the following would probably be true about this system? Explain each briefly. (8)

A.The AD and DBD cannot truly be considered “domains

Explanation / Answer

A transcriptional activator is also a protein that increases the gene transcription of a gene or a set of genes. Most activators are DNA-binding proteins that bind to enhancers or promoter-proximal elements.

Most activators function by binding sequence-specifically to a DNA site located in or near a promoter and making protein-protein interactions with the general transcription machinery (RNA polymerase and general transcription factors), this facilitates the binding of the transcription machinery to the promoter. The DNA site bound by the activator is referred to as an "activator site".

The part of the activator that makes protein-protein interactions with the general transcription machinery is referred to as an "activating region". The part of the general transcription machinery that makes protein-protein interactions with the activator is referred to as an "activation target".

Transcription factors perform this function alone or with other proteins in a complex, by promoting (activator), or blocking (repressor) the recruitment of RNA polymerase (the enzyme that performs the transcription of genetic information from DNA to RNA) to specific genes.

A unique feature of transcription factors is that they do contain one or more DNA-binding domains (DBDs), which attach to specific sequences of DNA adjacent to the genes that they regulate. Additional proteins such as coactivators, chromatin remodelers, histone acetylases, deacetylases, kinases, and methylases, while also playing crucial roles in gene regulation, lack DNA-binding domains, and, therefore, are not classified as transcription factors but do help in connecting or passing information between the two domains of transcriptional factors.

Transcription factors are modular in structure and contain the following domains:

DNA-binding domain (DBD), which attach to specific sequences of DNA (enhancer or Promoter: Necessary component for all vectors: used to drive transcription of the vector's transgene promotersequences) adjacent to regulated genes. DNA sequences that bind transcription factors are often referred to as response elements.

Trans-activating domain (TAD or AD), which contain binding sites for other proteins such as transcription coregulators. These binding sites are frequently referred to as activation functions (AFs).

An optional signal sensing domain (SSD) (e.g., a ligand binding domain), which senses external signals and, in response, transmits these signals to the rest of the transcription complex, resulting in up- or down-regulation of gene expression. Also, the DBD and signal-sensing domains may reside on separate proteins that associate within the transcription complex to regulate gene expression. this is the connection between the two domains, though the domains are seperated and connected to different Y and Z proteins they may act as SSD and thus conduct external signal and transmit these to the restr of the transcriptional complexes.

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