Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2020 Oct 26;64(5):807-817.
doi: 10.1042/EBC20200001.

Structural insight into FANCI-FANCD2 monoubiquitination

Landing Li #  1   2 , Winnie Tan #  1   2 , Andrew J Deans  1   2
Affiliations
Review

Structural insight into FANCI-FANCD2 monoubiquitination

Landing Li et al. Essays Biochem. .

Abstract

The Fanconi anemia (FA) pathway coordinates a faithful repair mechanism for DNA damage that blocks DNA replication, such as interstrand cross-links. A key step in the FA pathway is the conjugation of ubiquitin on to FANCD2 and FANCI, which is facilitated by a large E3 ubiquitin ligase complex called the FA core complex. Mutations in FANCD2, FANCI or FA core complex components cause the FA bone marrow failure syndrome. Despite the importance of these proteins to DNA repair and human disease, our molecular understanding of the FA pathway has been limited due to a deficit in structural studies. With the recent development in cryo-electron microscopy (EM), significant advances have been made in structural characterization of these proteins in the last 6 months. These structures, combined with new biochemical studies, now provide a more detailed understanding of how FANCD2 and FANCI are monoubiquitinated and how DNA repair may occur. In this review, we summarize these recent advances in the structural and molecular understanding of these key components in the FA pathway, compare the activation steps of FANCD2 and FANCI monoubiquitination and suggest molecular steps that are likely to be involved in regulating its activity.

Keywords: DNA synthesis and repair; Fanconi anemia; biochemistry; enzyme activity; protein structure; ubiquitin ligases.

PubMed Disclaimer

Conflict of interest statement

The authors declare that there are no competing interests associated with the manuscript.

Figures

Figure 1
Figure 1. Overall structural comparisons of mFancI–FancD2 and hFANCI–FANCD2 bound to interstrand cross-linked DNA
(A) The same domain architecture is shared by FANCI and FANCD2 and is shown schematically above. (B) Structure of mouse (m)FancI–FancD2 (PDB ID: 3S4W) where the ubiquitination sites, Lys559 residue of FANCD2 and Lys522 residue of FANCI are shown in red sticks; FANCI phosphorylation sites are shown in blue sticks. Close-up view of FANCI phosphorylation sites, Ser555, Thr558 and Thr564 exposed on the heterodimer interface, and Ser595, Ser616 and Ser628 residues buried in the complex. (C) Structure of human (h)FANCI–FANCD2 bound to interstrand cross-linked DNA (PDB ID: 6VAA). FANCD2 is colored in violet, FANCI in cyan and DNA in orange. Abbreviation: CTD, C-terminal domain.
Figure 2
Figure 2. Overall structural comparison of FANCI–FANCD2, FANCI–FANCD2Ub and FANCIUb–FANCD2Ub
(A) Structure of singly monoubiquitinated human FANCI–FANCD2Ub (PDB ID: 6VAF). (B) Structure of dually monoubiquitinated human FANCI Ub–FANCD2 Ub (PDB ID: 6VAE). (C) Comparison of FANCI–FANCD2 (PDB ID: 6VAA) and di-ubiquitinated FANCI–FANCD2 (PDB ID: 6VAE). FANCD2 is colored in violet, FANCI in cyan, ubiquitin in red and DNA in orange.
Figure 3
Figure 3. Proposed activation mechanism of FANCIUb–FANCD2Ub filamentous array
(A) FANCD2 forms an inactive homodimer which is inaccessible to DNA binding. FANCI displaces one of the FANCD2 and assembles into the FANCI–FANCD2 heterodimer, which is the substrate for FA core complex E3 ligase and DNA binding. FANCD2 ubiquitination clamps FANCI–FANCD2 heterodimer on DNA, which further stimulates ubiquitination of FANCI to form protective array against DNA degradation by nucleases or deubiquitination by USP1:UAF1. (B) Comparison of FANCD2 homodimer (PDB ID: 6TNI) and apo-FANCI–FANCD2 heterodimer (PDB: 6VAD). (C) Negative-stained electron micrograph of apo-FANCI–FANCD2. (D) Negative-stained electron micrograph of di-ubiquitinated FANCI–FANCD2 filamentous arrays. FANCD2 is colored in blue or violet, FANCI in cyan, ubiquitin in red and DNA in orange.
Figure 4
Figure 4. Structure of asymmetric FA core complex and FANCA–FANCG subcomplex
(A) Schematic of the chicken FA core complex. The arrows indicate potential protein:protein interactions of FANCA/FAAP20, UBE2T E2 enzyme and FANCI–FANCD2. (B) Structure of chicken FA core complex (PDB ID: 6SRI). (C) Schematic of the human FA core complex, colored by protein(s). FANCB/FAAP100 – orange; FANCL – red; FANCG – purple; FANCC/E/F – cyan; FANCA – cyan; FANCA′ – lime; FANCG and FANCG′ – purple. (D) Structure of FANCA–FANCG complex (PDB ID: 6LHV). (E) Structure of FANCA CTD dimer (PDB ID: 6LHS).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Gluckman E., Broxmeyer H.E., Auerbach A.D., Friedman H.S., Douglas G.W., Devergie A. et al. . (1989) Hematopoietic reconstitution in a patient with Fanconi’s Anemia by means of umbilical-cord blood from an HLA-identical sibling. N. Engl. J. Med. 321, 1174–1178 10.1056/NEJM198910263211707 - DOI - PubMed
    1. Grewal S.S., Kahn J.P., MacMillan M.L., Ramsay N.K.C. and Wagner J.E. (2004) Successful hematopoietic stem cell transplantation for Fanconi anemia from an unaffected HLA-genotype-identical sibling selected using preimplantation genetic diagnosis. Blood 103, 1147–1151 10.1182/blood-2003-02-0587 - DOI - PubMed
    1. Río P., Navarro S., Wang W., Sánchez-Domínguez R., Pujol R.M., Segovia J.C. et al. . (2019) Successful engraftment of gene-corrected hematopoietic stem cells in non-conditioned patients with Fanconi anemia. Nat. Med. 25, 1396–1401 10.1038/s41591-019-0550-z - DOI - PubMed
    1. Sawyer S.L., Tian L., Kähkönen M., Schwartzentruber J., Kircher M., University of Washington Centre for Mendelian Genomics et al. . (2015) Biallelic mutations in BRCA1 cause a new Fanconi anemia subtype. Cancer Discov. 5, 135–142 10.1158/2159-8290.CD-14-1156 - DOI - PMC - PubMed
    1. Alter B.P., Rosenberg P.S. and Brody L.C. (2007) Clinical and molecular features associated with biallelic mutations in FANCD1/BRCA2. J. Med. Genet. 44, 1–9 10.1136/jmg.2006.043257 - DOI - PMC - PubMed

Publication types

MeSH terms

Substances