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. 2023 Feb 23;12(3):559. doi: 10.3390/antiox12030559

Figure 8.

Figure 8

The synthesis of DNA from RNA precursors (ribonucleotides, as ribonucleoside diphosphates, center) depends upon their reduction by RNR to produce 2′-deoxyribonucleotides. Electrons for reduction by RNR come from either TRX or GLRX, the reduced forms of which must be constantly regenerated by one of the two essential redox cycles that sustain DNA synthesis: the TRX and GLRX systems. The former requires the selenoprotein TXNRD1, and the latter, GSH, a product of GCLC. Both TXNRD1 and GCLC are targeted by Mpro, consistent with a viral strategy to inhibit DNA synthesis, to conserve the pool of ribonucleotides for increased virion production [33]. Significantly, in an opposing action, both of these targets are also upregulated at the mRNA level by 1,25-dihydroxyvitamin D3, which may contribute to the reported benefits of vitamin D in COVID-19 [5,6,57].