Transcription factors interact with DNA non-covalently and all non-covalent binding reactions are reversible. Typically, binding occurs through a variety of weak intermolecular forces (e.g hydrogen bonds, ion pairs, van der Waals interactions, hydrophobic effect) whose strength is on the order of the thermal energy of the system. Therefore, thermal fluctuations can supply enough energy to break the bonds between transcription factor and DNA, releasing the transcription factor from the DNA.