Transcription of
insulin
Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabol ...
is regulated by the binding of various
transcription factor
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...
s to the ~400
base pair
A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...
s before the insulin transcription start site, called the "insulin regulatory sequence".
This sequence is made up of several distinct regions with different biochemical properties, each of which serve as binding sites for distinct regulatory proteins. First, multiple
A/
T-rich sequences, called "A elements", each of which contains a "TAAT" reocognized by
homeodomain proteins. These regions are primarily bound by
PDX-1, but also
Cdx2 and
Isl-1.
[ Second, two so-called "C elements" – C1 located 107–118 base pairs before the transcription start site; C2 311–317 base pairs before the start site. C1 is bound by RIPE3b1 via MafA. C2 (also called the "pancreatic islet cell enhancer sequence" or "PISCES") is bound by PAX6.][ Third, an "E element" (two in rodents) with sequence GCCATCTG is 91–100 base pairs before the transcription start site and binds the helix-loop-helix transcription factors NEUROD1.][ Lastly, several "cyclic AMP response elements" with sequence TGACGTCA that binds ]CREB
CREB-TF (CREB, cAMP response element-binding protein) is a cellular transcription factor. It binds to certain DNA sequences called cAMP response elements (CRE), thereby increasing or decreasing the transcription of the genes. CREB was first des ...
.[
In humans, a "Z-element" resides 243–292 base pairs before the start site and binds a complex called ZaI, as well as PDX-1 and MafA.][
]
References
{{Reflist
Regulatory sequences
Insulin