Proteasomal degradation restricts the nuclear lifespan of AID

Aoufouchi, Saïd; Faili, Ahmad; Zober, Carole; D’Orlando, Orietta; Weller, Sandra; Weill, Jean‐Claude; Reynaud, Claude‐Agnès

doi:10.1084/jem.20070950

Cited by 134 publications

(119 citation statements)

References 56 publications

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“…Thus, with regard to the alanine-scanning mutagenesis and consistent with the recent work of Aoufouchi et al (13), mutation of the hydrophobic residues (L189, F193, L196, L198) that resulted in reduced nuclear export and CSR also led to reduced abundance; in contrast, mutation of R190, D191, R194, or T195 to alanine had little effect on localization, abundance, or CSR (see Fig. 4A).…”

Section: Sensitivity Of Csr To the Interdigitating Hydrophilic Residusupporting

confidence: 71%

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The stability of AID and its function in class-switching are critically sensitive to the identity of its nuclear-export sequence

Geisberger

Rada²,

Neuberger³

2009

Proc. Natl. Acad. Sci. U.S.A.

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The carboxyterminal region of activation-induced deaminase (AID) is required for its function in Ig class switch recombination (CSR) and also contains a nuclear-export sequence (NES). Here, based on an extensive fine-structure mutation analysis of the AID NES, as well as from AID chimeras bearing heterologous NESs, we show that while a functional NES is indeed essential for CSR, it is not sufficient. The precise nature of the NES is critical both for AID stabilization and CSR function: minor changes in the NES can perturb stabilization and CSR without jeopardizing nuclear export. The results indicate that the AID NES fulfills a function beyond simply providing a signal for nuclear export and suggest the possibility that the quality of exportin-binding may be critical to the stabilization of AID and its activity in CSR.activation-induced deaminase ͉ antibody diversification ͉ immunoglobulin class switching ͉ exportin ͉ nuclear transport A ctivation-induced deaminase (AID) plays a central role in antibody gene-diversification, triggering both somatic hypermutation (SHM) and class-switch recombination (CSR) by deaminating deoxycytidine residues within the Ig locus to yield deoxyuridine (1, 2).AID is largely found in the cytoplasm of activated B cells but shuttles between cytoplasm and nucleus (3-6). The C-terminal amino acids of AID comprise a nuclear-export sequence (NES): removal of this NES causes AID to be restricted to the nucleus, whereas its addition to a heterologous nuclear protein drives export of the fusion protein into the cytoplasm (3-5). The sequence of the AID C-terminus conforms well to the consensus established for substrates of the Crm1-dependent export machinery: in keeping with this, export mediated by the AID NES is sensitive to leptomycin B.Analysis of both clinical and contrived mutations in AID have revealed that the AID C-terminal region is also essential for its function in CSR, although not in SHM (7-9). The C-terminal mutations that interfere with AID's ability to potentiate CSR do not compromise its ability to deaminate deoxycytidine in biochemical or bacterial genetic assays. Thus, as previously suggested by others, either the nuclear/cytoplasmic shuttling of AID must be specifically required for CSR or, alternatively, factors specific for CSR must interact with the C-terminal region of AID in an area overlapping the NES (4, 5, 7-9).It was with a view to discriminating these possibilities that we embarked on a refined mutagenic dissection of the AID NES and investigated the ability of heterologous NESs to substitute for the AID NES. Our results suggest that although nuclear export is likely necessary for CSR, this is not the sole function of the AID C-terminal region, with the data raising the possibility that successful CSR depends on the precise quality of AID binding to exportin or a related protein. Results NES Function and CSR Correlate in Alanine-Scanning Mutagenesis.To ascertain whether there was a correlation between export activity and CSR, we performed an alanine-scanning mut...

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Section: Sensitivity Of Csr To the Interdigitating Hydrophilic Residusupporting

confidence: 71%

“…The half-life of AID differs considerably, dependent on whether it is located in nucleus and cytoplasm (13). Indeed, fibroblasts transfected with the nuclear-restricted AID-GFP chimeras were usually less bright than those expressing the export-proficient proteins (see Fig.…”

Section: Sensitivity Of Csr To the Interdigitating Hydrophilic Residumentioning

confidence: 99%

The stability of AID and its function in class-switching are critically sensitive to the identity of its nuclear-export sequence

Geisberger

Rada²,

Neuberger³

2009

Proc. Natl. Acad. Sci. U.S.A.

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“…AID is rapidly degraded in the nucleus 19 , so altering the balance between the mechanisms determining its subcellular localization should influence its half-life. If cytoplasmic retention were important in determining the subcellular localization of AID in steady state, reduced retention of AID should lead to an increased proportion of nuclear protein, resulting in shorter protein half-life.…”

Section: Functional Impact Of Altering Aid Localization Balancementioning

confidence: 99%

“…This is highlighted by the cancer predisposition phenotype observed in transgenic mice overexpressing AID 7 , by the finding that ectopic SHM can occur in proto-oncogenes and tumor suppressor genes [8][9][10] and by the involvement of AID in oncogenic chromosomal translocations 11,12 . AID is normally induced in germinal center B cells 13 but in order to ensure that the genetic modifications it can cause are largely restricted to the Ig loci, there are multiple points of posttranscriptional regulation such as regulation of mRNA stability and translation [14][15][16] , subcellular localization 17,18 , protein stability 19 and modification by phosphorylation [20][21][22] .…”

Section: Introductionmentioning

confidence: 99%

Active nuclear import and cytoplasmic retention of activation-induced deaminase

Patenaude

Orthwein

et al. 2009

Nat Struct Mol Biol

133

175

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The enzyme Activation Induced Deaminase (AID) triggers antibody diversification in B-cells by catalyzing deamination and consequently mutation of immunoglobulin genes. To minimize off-target deamination, AID is restrained by several regulatory mechanisms including nuclear exclusion, thought to be mediated exclusively by active nuclear export. Here we identify two other mechanisms involved in controlling AID subcellular localization. AID is unable to passively diffuse into the nucleus, despite its small size, its nuclear entry requiring active import mediated by a conformational nuclear localization sequence (NLS). We also identify a determinant for AID cytoplasmic retention in its Cterminus, which hampers diffusion to the nucleus, competes with nuclear import and is critical for maintaining the predominantly cytoplasmic localization of AID in steady-state conditions. Blocking nuclear import alters the balance between these processes in favor of cytoplasmic retention, resulting in reduced isotype class switching.3

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“…Because AID is expressed throughout the cell cycle 105 , this attack can occur in the different phases of the cell cycle. Uracils generated during the G1 phase are preferentially recognized as U-G mismatches by the MSH2-MSH6 complex.…”

Section: A Model For Shm: Two Competitive Rather Than Alternative Patmentioning

confidence: 99%

DNA polymerases in adaptive immunity

Weill

Reynaud

2008

Nat Rev Immunol

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PrefaceTo cope with an unpredictable variety of potential pathogenic insults, the immune system must generate an enormous diversity of recognition structures, and it does so by making stepwise modifications of key genetic loci in each lymphoid cell. This proceeds through the action of lymphoid-specific proteins acting together with the general DNA-repair machinery of the cell. Strikingly, these general mechanisms are usually diverted from their normal functions, being used in rather atypical ways in order to privilege diversity over accuracy. In this Review, we focus on the contribution of a set of DNA polymerases discovered in the last decade to these unique DNA transactions.

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Proteasomal degradation restricts the nuclear lifespan of AID

Cited by 134 publications

References 56 publications

The stability of AID and its function in class-switching are critically sensitive to the identity of its nuclear-export sequence

The stability of AID and its function in class-switching are critically sensitive to the identity of its nuclear-export sequence

Active nuclear import and cytoplasmic retention of activation-induced deaminase

DNA polymerases in adaptive immunity

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