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Transcriptional repressor CTCF also known as 11-zinc finger protein or CCCTC-binding factor is a transcription factor that in humans is encoded by the CTCF gene. [ 5 ] [ 6 ] CTCF is involved in many cellular processes, including transcriptional regulation , insulator activity, V(D)J recombination [ 7 ] and regulation of chromatin architecture.
CTCF protein is known to favourably bind to unmethylated sites, so it follows that methylation of CpG islands is a point of epigenetic regulation. [2] An example of this is seen in the Igf2-H19 imprinted locus where methylation of the paternal imprinted control region (ICR) prevents CTCF from binding. [ 13 ]
A topologically associating domain (TAD) is a self-interacting genomic region, meaning that DNA sequences within a TAD physically interact with each other more frequently than with sequences outside the TAD. [1] The average size of a topologically associating domain (TAD) is 1000 kb in humans, 880 kb in mouse cells, and 140 kb in fruit flies.
This process continues until the extruding complex is released or encounters a barrier. In vertebrates, one well-studied factor that limits loop extrusion by cohesin is the CCCTC-binding factor (CTCF). CTCF directly interacts with cohesin, stabilizing it on chromatin and anchoring loop boundaries.
So does the father's allele, but in his case, the insulator has been methylated. CTCF can no longer bind to the insulator, and so the enhancer is now free to turn on the father's IGF2 promoter. [7] The canonical isoform of IGF-2 preproprotein (180 amino acids) includes a signal peptide (amino acids 1-24) and a propeptide (amino acids 92-180).
CTCF molecules can form homodimers on DNA, which can be co-bound by cohesin; this chromatin loop structure helps constrain the ability of enhancers within the loop to target genes outside the loop. Loops with CTCF and cohesin at the start and end of the loop that restrict enhancer-gene targeting are "insulated neighborhoods."
CCCTC-binding factor (CTCF) is a zinc finger protein which occurs naturally in some human cells. CTCF is localized to the nucleus of cells. CTCF is localized to the nucleus of cells. CTCF has been shown [ 6 ] to naturally regulate the expression of human linear dsDNA by binding with target DNA sequences or motifs .
Furthermore, CTCF is often found at self-interacting domain boundaries, and can anchor the chromatin to the nuclear lamina. [19] CTCF is also involved in V(D)J recombination. [20] Cohesin: The cohesin complex was initially discovered as a key player in mitosis, binding sister chromatids together to ensure proper segregation.