Human Tribbles 3 protects nuclear DNA from cytidine deamination by APOBEC3A.

Institut Pasteur, France.
Journal of Biological Chemistry (Impact Factor: 4.6). 09/2012; DOI: 10.1074/jbc.M112.372722
Source: PubMed

ABSTRACT The human polydeoxynucleotide cytidine deaminases APOBEC3A, APOBEC3C and APOBEC3H are capable of mutating viral DNA in the nucleus, while APOBEC3A alone efficiently edits nuclear DNA. Deamination is rapidly followed by excision of uracil residues and can lead to double strand breaks. It is not known to which protein networks these DNA mutators belong. Using a yeast two-hybrid screen, we identified the human homologue 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 while 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 strand breaks. The interaction results in degradation of A3A in a proteasome independent manner. TRIB3 has been linked to cancer and via it own interactors, links the A3A DNA mutators to the Rb-BRCA1-ATM network. TRIB3 emerges as an important guardian of genome integrity.

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Available from: Frederic Tangy, Jul 08, 2015
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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 · 4.82 Impact Factor
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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 · 14.31 Impact Factor
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    ABSTRACT: APOBEC3A (A3A) is a myeloid lineage specific DNA cytosine deaminase with a role in innate immunity to foreign DNA. Previous studies have shown that heterologously expressed A3A is genotoxic, suggesting that monocytes may have a mechanism to regulate this enzyme. Indeed, we observed no significant cytotoxicity when interferon was used to induce the expression of endogenous A3A in CD14+-enriched primary cells or the monocytic cell line THP-1. In contrast, doxycycline-induced A3A in HEK293 cells caused major cytotoxicity at protein levels lower than those observed when CD14+ cells were stimulated with interferon. Immunofluorescent microscopy of interferon stimulated CD14+ and THP-1 cells revealed that endogenous A3A is cytoplasmic, in stark contrast to stably or transiently transfected A3A, which has a cell wide localization. A3A constructs engineered to be cytoplasmic are also non-toxic in HEK293 cells. These data combine to suggest that monocytic cells use a cytoplasmic retention mechanism to control A3A and avert genotoxicity during innate immune responses.
    Journal of Biological Chemistry 05/2013; DOI:10.1074/jbc.M113.458661 · 4.60 Impact Factor