What is the Principle of the Disc Insulator?

Ⅰ. What is Disc insulator?

Disc insulator is generally made of insulating parts (such as porcelain parts) and metal accessories (such as steel feet, iron caps and flanges) glued with glue or mechanically clamped. It is widely used in power systems and generally belongs to external insulation and operates under atmospheric conditions. Overhead transmission lines, bus bars of power plants and substations, and external live conductors of various electrical equipment must be supported by insulators. 

Ⅱ. Working principle of disc insulator

1. Some enhancers are located upstream of the promoter and some are located downstream, so the effect of the disc insulator does not depend on the relative orientation of the insulator and the promoter. Therefore, the reason for the directionality of the insulator effect has not really been clarified.

2. It has been found that there are two loci that affect the function of disc insulators by trans-activation. The nucleoprotein encoded by the gene S2J (Hw) recognizes the insulator, and the insulator has an insulating effect only after it is combined with it. When the gene is mutated, although an insulator is inserted in the y locus, the insulating effect is lost, and y is expressed in all tissues.

3. The other locus is mod. After that gene is mutated, its effect is just opposite to that of Su, that is, these mutants all enhance the insulating effect, so that the insulating effect of the insulator is not  directional but expanding. It blocked the effect of enhancers at the upstream and downstream ends.

There is a kind of explanation that the electrical power insulator has an insulating effect after Su is first combined with the insulator DNA. Mod (mdg4) is combined with Su (Hw) to make the insulator lose its insulation effect; the abrupt mod (mdg4) cannot be combined with Su (Hw), so the insulator enhances the insulation effect.