Week 7 Flashcards
How do transcription factors distinguish specific DNA sequences in a genome with vast non-specific DNA?
Transcription factors recognize specific DNA motifs through their DNA-binding domains by forming hydrogen bonds and van der Waals contact in the major groove. binding specificity is enhanced by cooperative interactions and chromatin accessibility.
What is a pioneer transcription factor, and how does it differ from other transcription factors?
Pioneer factors such as FOXA1 can bind to their target DNA sequences within condensed chromatin and initiate chromatin remodeling, making the region accessible to other transcription factors and cofactors.
What type of DNA binding domains are on transcription factors?
Zinc fingers, leucine zippers and homeodomains
Describe the concept of a transcription factor “combinational control”
Combinational control refers to the integration of multiple transcription factors at a gene’s regulatory regions, allowing complex and context-specific gene expression patterns from a limited number of TFs.
What is an enhanceosome, and how does it contribute to transcriptional activation?
An enhanceosome is a higher-order protein complex formed by transcription factors and coactivators at an enhancer region. It creates a precise 3D configuration required for efficient recruitment of the transcriptional machinery.
How does post translational modification affect transcription factor activity?
PTMs like phosphorylation, acetylation or ubiquitination can alter their activity and their localization and stability. For example phosphorylation of CREB by PKA enhances its binding to CBP and promotes transcription.
How can transcription factors function as both activators and repressors?
The function of TFs depend on cell type, cofactors, chromatin state, and target gene context. For instance, REST represses neuronal genes in non-neuronal cells but is inactive in neurons, allowing expression.
Explain how transcription factors interact with coactivators an corepressors.
Transcription factors recruit coactivators (p300) to promote chromatin opening o corepressors (NCoR) to condense chromatin. These interactions modulate histone modifications and influence transcriptional outcomes.
What is a response element and how does it relate to inducible gene expression?
A response element element is a short DNA sequence in a promoter or enhancer that binds a specific transcription facotr in response to a signal for example, GREs (glucocorticoid response elements) bind the glucocorticoid receptor upon hormone stimulation.
How do transcription factors contribute to cell fate decisions during development?
Lineage-determining transcription factors activate gene programs specific to a cell type while repressing alternative lineages. their expression is tightly regulated spatially and temporally, creating feedback loops and epigenetic memory.
