Section 2: Classes of Transcription Factors

What are General Transcription Factors?

General transcription factors (e.g., TFIID, TBP) are expressed in all cell types and form the pre-initiation complex to initiate transcription at RNA Polymerase II genes.

What does TFIID bind to?

TFIID binds to the TATA box, which is found in the majority of protein-coding gene promoters.

What are Lineage-Specific Transcription Factors?

Lineage-specific transcription factors (e.g., HOXD13, KLF4, MYOD) are expressed only in specific cell types, bind to accessible chromatin, and recruit co-activators or co-repressors to regulate cell-type-specific gene expression.

Why are Lineage-Specific Transcription Factors important?

They coordinate gene expression programs and cell fate decisions, making them critical for directing cell identity and differentiation.

What are Pioneer Transcription Factors?

Pioneer transcription factors (e.g., SOX2, FOXA1, PAX7) have the capacity to bind to inaccessible regions of DNA that are occupied by nucleosomes, which most transcription factors cannot do.

What do Pioneer Transcription Factors do after binding?

They recruit chromatin remodelers to alter chromatin structure and open up the DNA for other transcription factors.

Why are Pioneer Transcription Factors important in development?

They are a key step in many cell fate transitions, such as from stem cells to lineage-committed cells.

What are Nuclear Receptor Transcription Factors?

Nuclear receptor transcription factors (e.g., Estrogen Receptor, Androgen Receptor, Retinoic acid receptor) have induced DNA-binding activity after binding a ligand.

How do Nuclear Receptor Transcription Factors respond to signals?

Ligand binding can induce transport of the receptor from the cytoplasm to the nucleus, allowing transcription to rapidly adapt to metabolic stress, hormone changes, or other signalling events.

What is the additional function of many ligand-binding domains in nuclear receptors?

Many ligand-binding domains are also involved in dimerisation of the nuclear recepto