Transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...

insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the ''INS'' gene. It is considered to be the main anabolic hormone of the body. It regulates the metabolism o ...

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 of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The fu ...

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 protein A homeobox is a DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. For instance, mutations in a homeobox may change large-scale anatomical features of the full ...

s. These regions are primarily bound by

PDX-1 PDX1 (pancreatic and duodenal homeobox 1), also known as insulin promoter factor 1, is a transcription factor in the ParaHox gene cluster.Brooke, N. M., Garcia-Fernàndez, J., & Holland, P. W. (1998). The ParaHox gene cluster is an evolutionary si ...

, but also Cdx2 and

Isl-1 Insulin gene enhancer protein ISL-1 is a protein that in humans is encoded by the ''ISL1'' gene. Function This gene encodes a transcription factor containing two N-terminal LIM domains and one C-terminal homeodomain. The encoded protein play ...

. 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 Transcription factor Maf also known as proto-oncogene c-Maf or V-maf musculoaponeurotic fibrosarcoma oncogene homolog is a transcription factor that in humans is encoded by the ''MAF'' gene. Types One type, ''MafA'', also known as ''RIPE3b1'', pr ...

via MafA. C2 (also called the "pancreatic islet cell enhancer sequence" or "PISCES") is bound by

PAX6 Paired box protein Pax-6, also known as aniridia type II protein (AN2) or oculorhombin, is a protein that in humans is encoded by the ''PAX6'' gene. Function PAX6 is a member of the Pax gene family which is responsible for carrying the geneti ...

. 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 Neurogenic differentiation 1 (Neurod1), also called β2, is a transcription factor of the NeuroD-type. It is encoded by the human gene NEUROD1. In mice, ''Neurod1'' expression is first seen at embryonic day 12 (E12). It is a member of the Neurod ...

. Lastly, several "cyclic AMP response elements" with sequence TGACGTCA that binds CREB. 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