TRF2-binding region of apollo and similar proteins
Apollo protein, a DNA repair nuclease, is recruited to telomeres by TRF2 where it is associated with the principle components of the shelterin complex. Apollo is a member of the metallo-beta-lactamase family that is required for telomere integrity during S phase; its 5' exonuclease activity is regulated by binding to TRF2. Apollo and TRF2 also suppress damage to engineered interstitial telomere repeat tracts at the chromosome ends. TRF2, which binds preferentially to positively supercoiled DNA substrates, together with Apollo, negatively regulates the amount of DNA topoisomerases (TOP1, TOP2-alpha, and TOP2-beta) at telomeres since they also act in the same pathway of telomere protection. The shelterin complex protein identified in mammals is principally comprised of 6 factors that act to protect telomeres from DNA damage repair machinery. 3 components (TRF1, TRF2, POT1) bind DNA and 3 components are recruited by these factors (TIN2, RAP1, TPP1).
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