The iron chaperone and nucleic acid–binding activities of poly(rC)-binding protein 1 are separable and independently essential

Abstract

Poly(rC)-binding protein (PCBP1) is a multifunctional adaptor protein that can coordinate single-stranded nucleic acids and iron–glutathione complexes, altering the processing and transfer of these ligands through interactions with other proteins. Multiple phenotypes are ascribed to cells lacking PCBP1, but the relative contribution of RNA, DNA, or iron chaperone activity is not consistently clear. Here, we report the identification of amino acid residues required for iron coordination on each structural domain of PCBP1 and confirm the requirement of iron coordination for binding target proteins BolA2 and ferritin. We further construct PCBP1 variants that lack either nucleic acid– or iron-binding activity and examine their functions in human cells and mouse tissues depleted of endogenous PCBP1. We find that these activities are separable and independently confer essential functions. While iron chaperone activity controls cell cycle progression and suppression of DNA damage, RNA/DNA-binding activity maintains cell viability in both cultured cell and mouse models. The coevolution of RNA/DNA binding and iron chaperone activities on a single protein may prove advantageous for nucleic acid processing that depends on enzymes with iron cofactors.

Ferroptosis turns 10: Emerging mechanisms, physiological functions, and therapeutic applications

“…The depletion of GSH can not only inactivate GPX4 but also mobilize Fe(II) for Fenton chemistry, promoting the propagation of lipid peroxides and ultimately ferroptosis. In addition, iron storage in ferritin requires the formation of the GSH-iron complex, which is delivered to ferritin via the chaperone poly(rC) binding protein 1 (PCBP1) (Patel et al, 2021). Thus, depletion of GSH promotes the availability of labile iron.…”

Heterogeneous nuclear ribonucleoprotein E1 binds polycytosine DNA and monitors genome integrity

“…In the absence of hnRNP E1, repair at poly-C sites slows down because signaling and loading of repair proteins is slow; however, other proteins such as RPA carry out the functions of hnRNP E1 directly at these sites in DNA repair. While the manuscript was being revised a new publication showed that the iron-binding and DNA damage functions are separable from RNA binding functions ( Patel et al, 2021 ); the authors also suggested that the nucleic acid and iron binding by hnRNP E1 might enhance the assembly or repair of iron cofactors in DNA- and RNA-modifying enzymes. Although this is a major possibility in untreated E1KD cells, we predict the existence of additional possibilities; in addition, sensing and repair of genotoxin-induced DNA damage may involve different mechanism.…”

The Role of Ferritin in Health and Disease: Recent Advances and Understandings

“…In addition to regulating intracellular iron trafficking, PCBPs are involved in post-transcriptional gene regulation, maintenance of mitochondrial stability, and are associated with a wide variety of pathophysiologies such as rheumatoid arthritis [ 37 ], amyotrophic lateral sclerosis (ALS) [ 38 ], and Huntington’s disease (HD), and certain neurodevelopmental disorders [ 39 ]. Although the iron chaperone and RNA-binding functions of PCBPs have been shown to be independently essential [ 40 ], it is not clear how these functions potentially contribute to the pathogenesis of the above-mentioned disorders.…”