Locus Control Region
Encyclopedia
Locus control regions are defined by their ability to enhance the expression of linked genes to physiological levels in a tissue-specific and copy number-dependent manner at ectopic chromatin
sites. The concept derives from the idea that developmental and cell lineage-specific regulation of gene expression relies not only on gene-proximal elements such as promoters, enhancer
s, and silencer
s, but also on long-range interactions of various cis-regulatory elements and dynamic chromatin alterations.
The LCR was identified over 20 years ago. In transgenic mouse studies it was determined that the LCR was required for normal regulation of beta-globin
gene expression. Several models exist for how the LCR exerts its effects on transcription from a distance.
Looping model: LCR section of the DNA loops around to different extent over the desired gene of expression, so that the binding site of the transcriptional machinery (proteins) is in physical close proximity to bridge and affect the transcription of that specific gene.
Chromatin
Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are; to package DNA into a smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and prevent DNA damage, and to control gene...
sites. The concept derives from the idea that developmental and cell lineage-specific regulation of gene expression relies not only on gene-proximal elements such as promoters, enhancer
Enhancer (genetics)
In genetics, an enhancer is a short region of DNA that can be bound with proteins to enhance transcription levels of genes in a gene cluster...
s, and silencer
Silencer (DNA)
In genetics a silencer is a DNA sequence capable of binding transcription regulation factors termed repressors. Upon binding, RNA polymerase is prevented from initiating transcription thus decreasing or fully suppressing RNA synthesis....
s, but also on long-range interactions of various cis-regulatory elements and dynamic chromatin alterations.
The LCR was identified over 20 years ago. In transgenic mouse studies it was determined that the LCR was required for normal regulation of beta-globin
Beta globulins
Beta globulins are a group of globular proteins in plasma thatare more mobile in alkaline or electrically charged solutions than gamma globulins, but less mobile than alpha globulins. Beta globin is on chromosome 11.Examples of beta globulins include:...
gene expression. Several models exist for how the LCR exerts its effects on transcription from a distance.
Looping model: LCR section of the DNA loops around to different extent over the desired gene of expression, so that the binding site of the transcriptional machinery (proteins) is in physical close proximity to bridge and affect the transcription of that specific gene.