Abstract:

The formation of a DNA loop takes a crucial role in transcriptional regulation, where the enhancer is tethered to its promoter. This step is a time-limiting step for activating transcriptional initiation. Here, We review a formula that is appropriate for computing the time required for formatting such a loop, or other DNA loops at the similar length scale where the looping can be attributed to a spontaneous decrease in conformation entropy. The formula shows that topological structure due to the orientation of two big grooves where a protein binds primarily determines whether two sites could be looped, and that the intervening DNA length denes the looping time. This method takes the advantages of bypassing the complexity of DNA structure and cellular circumstances, but requiring some parameters to be measured experimentally.

Key words: rigidity and , exibility, conformation entropy, topological structure