Question

Describe the features of AP-1 members that make them unique amongst transcriptional activators

Describe how the activation of Gs protein receptors, tyrosine kinase receptors and ligand-gated calcium ion channels can lead to changes in c-fos gene transcription

Answer 1

AP-1 refers to Activating protein 1, its a transcription factor , a heterodimeric one,made up of proteins that belong to c-Fos, c-Jun, ATF,JDP families.It plays a key role in regulation of neural genes, neutrophils, osteoblast differentiation,apoptosis and more.AP-1's activity id dependent upon the specific amounts of Jun/Fos factors present in a cell.Jun and/or Fos factors bind to AP-1 consensus sequence on the DNA as hetero or homo dimers.

c-Fos is a proto-oncogene, and comprises a basic zipper region for dimerization.A variety of external stimuli like UV radiation, growth factors etc. It can form heterodimers mostly with jun family of proteins.

Calcium and cAMP mediate c-fos transcription via some common transcription factors.Influx of calcium in the cell via ligand gated ion channels that open in response to membrane depolarization or high levels of c-AMP triggered by G-protein coupled receptors which are inturn activated by neurotransmitters/hormones, leading to activation of c-AMP dependent protein kinases that phosphorylates CREB (CRE binding protein) on serine 133 position. Both pathways converge on CREB phosphorylation which binds to CRE element on DNA and mediates c-Fos transcription.