Human tribbles 3 protects nuclear DNA from cytidine deamination by APOBEC3A

Institut Pasteur, France.
Journal of Biological Chemistry (Impact Factor: 4.57). 09/2012; 287(46). DOI: 10.1074/jbc.M112.372722
Source: PubMed


The human polydeoxynucleotide cytidine deaminases APOBEC3A, APOBEC3C, and APOBEC3H are capable of mutating viral DNA in the
nucleus, whereas APOBEC3A alone efficiently edits nuclear DNA. Deamination is rapidly followed by excision of uracil residues
and can lead to double-stranded breaks. It is not known to which protein networks these DNA mutators belong. Using a yeast
two-hybrid screen, we identified the human homolog of Drosophila Tribbles 3, TRIB3, as an interactor for APOBEC3A and APOBEC3C. The interaction was confirmed by co-affinity purification.
Co-transfection of APOBEC3A with a TRIB3 expression vector reduced nuclear DNA editing whereas siRNA knockdown of TRIB3 increased the levels of nuclear DNA editing, indicating that TRIB3 functioned as a repressor of A3A. It also repressed A3A-associated
γH2AX positive double-stranded breaks. The interaction results in degradation of A3A in a proteasome-independent manner. TRIB3
has been linked to cancer and via its own interactors and links the A3A DNA mutators to the Rb-BRCA1-ATM network. TRIB3 emerges
as an important guardian of genome integrity.

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    • "These APOBEC3 mutator enzymes must be tightly controlled as at least four (A3A, A3B, A3C and A3H) can access the nucleus (Vartanian et al, 2008; Stenglein et al, 2010; Landry et al, 2011; Suspène et al, 2011a; Aynaud et al, 2012; Shinohara et al, 2012; Burns et al, 2013a, b). More recently, it has emerged that APOBEC3A (A3A) and probably APOBEC3B (A3B) can mutate nuclear DNA (nuDNA) (Suspène et al, 2011a; Aynaud et al, 2012; Shinohara et al, 2012; Burns et al, 2013a). A3A can edit both cytidine and 5-methylcytidine residues in ssDNA (Carpenter et al, 2012; Wijesinghe and Bhagwat, 2012; Suspène et al, 2013) and can generate DNA double-strand breaks (Landry et al, 2011; Mussil et al, 2013). "
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    ABSTRACT: Background: The revolution in cancer genomics shows that the dominant mutations are CG->TA transitions. The sources of these mutations are probably two host cell cytidine deaminases APOBEC3A and APOBEC3B. The former in particular can access nuclear DNA and monotonously introduce phenomenal numbers of C->T mutations in the signature 5′TpC context. These can be copied as G->A transitions in the 5′GpA context. Methods: DNA hypermutated by an APOBEC3 enzyme can be recovered by a technique called 3DPCR, which stands for differential DNA denaturation PCR. This method exploits the fact that APOBEC3-edited DNA is richer in A+T compared with the reference. We explore explicitly 3DPCR error using cloned DNA. Results: Here we show that the technique has a higher error rate compared with standard PCR and can generate DNA strands containing both C->T and G->A mutations in a 5′GpCpR context. Sequences with similar traits have been recovered from human tumour DNA using 3DPCR. Conclusions: Differential DNA denaturation PCR cannot be used to identify fixed C->T transitions in cancer genomes. Presently, the overall mutation frequency is ∼104–105 base substitutions per cancer genome, or 0.003–0.03 kb−1. By contrast, the 3DPCR error rate is of the order of 4–20 kb−1 owing to constant selection for AT DNA and PCR-mediated recombination. Accordingly, sequences recovered by 3DPCR harbouring mixed C->T and G->A mutations associated with the 5′GpC represent artefacts.
    British Journal of Cancer 04/2014; 110(10). DOI:10.1038/bjc.2014.176 · 4.84 Impact Factor
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    • "TRB3 may also play a role in cell cycle control, cell survival, DNA repair, and genome stability by interacting with Ct interacting protein (CtIP) [154] and polydeoxynucleotide cytidine deaminases APOBEC3A and APOBEC3C. These interactions inhibit nuclear DNA editing, suggesting that TRB3 may be an important guardian of genome integrity [164]. "
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    ABSTRACT: In 2000, investigators discovered Tribbles, a Drosophila protein that coordinates morphogenesis by inhibiting mitosis. Further work has delineated Xenopus (Xtrb2), Nematode (Nipi-3), and mammalian homologs of Drosophila tribbles, which include TRB1, TRB2, and TRB3. The sequences of tribbles homologs are highly conserved, and despite their protein kinase structure, to date they have not been shown to have kinase activity. TRB family members play a role in the differentiation of macrophages, lymphocytes, muscle cells, adipocytes, and osteoblasts. TRB isoforms also coordinate a number of critical cellular processes including glucose and lipid metabolism, inflammation, cellular stress, survival, apoptosis, and tumorigenesis. TRB family members modulate multiple complex signaling networks including mitogen activated protein kinase cascades, protein kinase B/AKT signaling, mammalian target of rapamycin, and inflammatory pathways. The following review will discuss metazoan homologs of Drosophila tribbles, their structure, expression patterns, and functions. In particular, we will focus on TRB3 function in the kidney in podocytes. This review will also discuss the key signaling pathways with which tribbles proteins interact and provide a rationale for developing novel therapeutics that exploit these interactions to provide better treatment options for both acute and chronic kidney disease.
    12/2013; 2013(9843):750871. DOI:10.1155/2013/750871
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    • "Following cytidine deamination of nuDNA, UNG excision of uracil bases and subsequent APE1 cleavage of the DNA backbone at abasic sites can result in DSBs characterized by gH2AX phosphorylation (Rogakou et al. 1998). Although well established for AID, it has recently been shown to occur following human A3A deamination (Landry et al. 2011; Aynaud et al. 2012). As most mammalian A3A enzymes can deaminate, nuDNA induction of gH2AX positive DSBs was assessed for all A3A proteins. "
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    ABSTRACT: The human APOBEC3 gene cluster locus encodes polynucleotide cytidine deaminases While several act as viral restriction factors through mutation of single stranded DNA, recent reports have shown that human APOBEC3A was capable of efficiently hypermutating nuclear DNA and inducing DNA breaks in genomic DNA. In addition the enzyme was unique in efficiently deaminating 5-methylcytidine in single stranded DNA. To appreciate the evolutionary relevance of these activities, we analysed A3A related enzymes from the rhesus and tamarin monkey, horse, sheep, dog and panda. All proved to be orthologous to the human enzyme in all these activities revealing strong conservation over ∼148 million years. Hence, their singular role in DNA catabolism is a well-established mechanism probably outweighing any deleterious or pathological roles such as genomic instability and cancer formation.
    Molecular Biology and Evolution 10/2013; 31(2). DOI:10.1093/molbev/mst195 · 9.11 Impact Factor
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