Specific Mg2+ binding to AT-rich regions of chromatin in the evolution of eukaryotes

At SIMS XIV, we reported SIMS evidence of specific Mg2+ binding to the AT-rich regions of human metaphase chromosomes represented by G-bands. Subsequent Mg2+-depletion experiments supported a direct role for Mg2+ in promoting and maintaining the higher order chromatin structure originating G-bands, possibly due to both Mg2+-DNA and Mg2+-protein interactions. An in-depth study, reported elsewhere, implicated also Ca2+ in the maintenance of chromatin ultrastructure in the scaffold of mammalian chromosomes, in association with topoisomerase II.