5′ flanking region

Source: Wikipedia, the free encyclopedia.

The 5′ flanking region is a region of

gene transcription. 5′ flanking regions are categorized between prokaryotes and eukaryotes
.

Structure of a eukaryotic gene. 5′ flanking region is shown in yellow on the left of the DNA strand. Since it is not transcribed, it is no longer present in the RNA or protein form.

Eukaryotic elements

In eukaryotes, the 5′ flanking region has a complex set of regulatory elements such as

downstream core promoter element, CAAT box, and the GC box.[1]

Enhancer

Enhancers are DNA sequences found in 5′ flanking regions of eukaryotic genes that affect transcription. If a

transcription start site, they can be present anywhere on or around the gene of interest.[3]

Silencer

Silencers are DNA sequences found in the 5′ flanking region of eukaryotic genes, assisting in the silencing of a gene. They can be found upstream, downstream, or within the gene of interest.[3] When repressors bind silencers, they act in a similar fashion as enhancers and bend over to prevent the interaction of RNA polymerase with promoters. This silences the gene and therefore the gene will not be expressed in the cell.

TATA box

The TATA box is present in all genes that are transcribed by RNA polymerase II, which is most eukaryotic genes. The binding of the TATA box with TATA binding protein initiates the formation of a transcription factor complex. This is followed by binding of transcription factor TFIID, which then recruits TFIIB, TFIIF, RNA polymerase II and TFIIH (in that order) to form an initiation complex.[1] It is typically 10 nucleotides long, and is present -30 to -20 nucleotides upstream from the transcription start site, in the core promoter region.[2]

CAAT box

The CAAT box is a crucial element of the 5′ flanking region of eukaryotic genomes. A specific transcription factor called

proximal promoter region.[2]

Prokaryotic elements

Prokaryotes only have three promoter elements: two elements are present -35 and -10 nucleotides upstream of the transcription start site, and the third is directly upstream the transcription start site. Prokaryotic promoter elements are not identical among species, but have a consensus sequence of 6 nucleotides each. Bacterial RNA polymerase binds to these regions to align itself and begin transcription. Promoter sequences that differ from the consensus sequence are generally transcribed less efficiently. Additionally, induced mutations in these -35 and -10 promoter sequences have proven to be deleterious to transcription.[4]

Polymorphisms

Flanking SNPs are

ADHD, schizophrenia and methamphetamine abuse.[7] Insertions and deletions in the 5′ flanking region of the insulin gene have been associated with type 2 diabetes.[8][9] Polymorphisms in the 5′ flanking region of the gene coding for oxytocin have been linked to mutations in promoter function, ultimately leading to potential disorders related to altered oxytocin levels and functionality.[10]

References

  1. ^ a b "Prokaryotic vs. Eukaryotic Transcription". www.chem.uwec.edu. Retrieved 2016-10-30.
  2. ^ a b c "Lecture 2". www.zoology.ubc.ca. Retrieved 2016-11-18.
  3. ^ a b Boundless (2016-05-26). "Transcriptional Enhancers and Repressors". Boundless. Archived from the original on 2016-12-21. Retrieved 2016-12-15.
  4. ^ Cooper, Geoffrey M. (2000-01-01). "Transcription in Prokaryotes". The Cell: A Molecular Approach (2nd ed.). Sinauer Associates.
  5. PMID 1778977
    .
  6. S2CID 21180258
    .
  7. S2CID 25019784
    .
  8. PMID 6292721
    .
  9. PMID 6267694
    .
  10. S2CID 10565518
    .
Retrieved from "https://en.wikipedia.org/w/index.php?title=5′_flanking_region&oldid=1163322009"