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3C technology  (Chromosome Conformation Capture): technology used to identify whether two known genomic regions interact (one vs one) . After the crosslinking of the two strands (formaldehyde), a digestion with a common restriction enzyme is performed (usually EcoRI, whose site is present once every 400 bases, as mean). Than, intramolecular ligation is carried out, using Ligase as ATP (MILD CONDITION, to avoid intermolecular ligation). Now a reverse crosslinking step is performed. A phenol-clorophorm purification should be done, to eliminate proteins present in the mixture (*). Now, with specific primers (pairing the two regions of interest) is possible to detect the interaction by simple PCR. 

4C-seq (Circularized Chromosome Conformation Capture): based on 3C technique, allows to identify the interaction(s) between a known genomic region and all other possible regions (one vs all). The first steps are the same of the 3C, until “*”. Now, a second digestion is performed, using likely a 4 bases cutting enzyme. The sticky ends produced will be then ligated together (Ligase and ATP) always under mild condition, forming a circular structure. Using primers of the known region a reverse PCR will be performed. The PCR products (library) will then be NGS sequenced to identify the interacting region(s). 

3. 5C and Hi-C

4. ChIA-PET