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AID can restrict L1 retrotransposition suggesting a dual role in innate and adaptive immunity.

MacDuff DA, Demorest ZL, Harris RS - Nucleic Acids Res. (2009)

Bottom Line: We found that AID can inhibit the retrotransposition of L1 through a DNA deamination-independent mechanism.This mechanism may manifest in the cytoplasmic compartment co- or posttranslationally.Together with evidence for AID expression in the ovary, our data combined to suggest that AID has innate immune functions in addition to its integral roles in creating antibody diversity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA.

ABSTRACT
Retrotransposons make up over 40% of the mammalian genome. Some copies are still capable of mobilizing and new insertions promote genetic variation. Several members of the APOBEC3 family of DNA cytosine deaminases function to limit the replication of a variety of retroelements, such as the long-terminal repeat (LTR)-containing MusD and Ty1 elements, and that of the non-LTR retrotransposons, L1 and Alu. However, the APOBEC3 genes are limited to mammalian lineages, whereas retrotransposons are far more widespread. This raises the question of what cellular factors control retroelement transposition in species that lack APOBEC3 genes. A strong phylogenetic case can be made that an ancestral activation-induced deaminase (AID)-like gene duplicated and diverged to root the APOBEC3 lineage in mammals. Therefore, we tested the hypothesis that present-day AID proteins possess anti-retroelement activity. We found that AID can inhibit the retrotransposition of L1 through a DNA deamination-independent mechanism. This mechanism may manifest in the cytoplasmic compartment co- or posttranslationally. Together with evidence for AID expression in the ovary, our data combined to suggest that AID has innate immune functions in addition to its integral roles in creating antibody diversity.

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Effect of a nuclear export-defective AID mutant on L1 retrotransposition. (A) Percentage of puromycin-resistant cells that were GFP-positive 5 days after transfection with the L1 and indicated AID variants. A3A and A3AE72A were included as controls. Histogram bars represent the mean of three independent cultures, and the standard deviation is shown. WT, wild-type. (B) Western blot showing expression of the HA-tagged proteins from a representative experiment from (A). Tubulin is a loading control. (C) E. coli-based RifR mutation assay. See the legend to Figure 3C for assay and label details. (D) Localization of GFP-tagged AID and AIDΔC in HeLa cells, in the presence and absence of leptomycin B. The scale bars represent 25 μM.
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Figure 4: Effect of a nuclear export-defective AID mutant on L1 retrotransposition. (A) Percentage of puromycin-resistant cells that were GFP-positive 5 days after transfection with the L1 and indicated AID variants. A3A and A3AE72A were included as controls. Histogram bars represent the mean of three independent cultures, and the standard deviation is shown. WT, wild-type. (B) Western blot showing expression of the HA-tagged proteins from a representative experiment from (A). Tubulin is a loading control. (C) E. coli-based RifR mutation assay. See the legend to Figure 3C for assay and label details. (D) Localization of GFP-tagged AID and AIDΔC in HeLa cells, in the presence and absence of leptomycin B. The scale bars represent 25 μM.

Mentions: Since L1 undergoes reverse transcription in the nucleus of the host cell, we initially hypothesized that AID would need to be in the nucleus to inhibit this process. However, since mutation of the L1 DNA by AID is not required to inhibit L1 replication, AID could be acting either within the nucleus or within the cytoplasm, where it is localized predominantly [(61); Figure 4D]. To address this question, we tested a variant of AID that is mostly nuclear because it lacks the last 10 amino acids, which includes the nuclear export sequence (AIDΔC) [(62,63); Figure 4D]. AIDΔC inhibited L1 to the same extent as the wild-type protein (Figure 4).Figure 4.


AID can restrict L1 retrotransposition suggesting a dual role in innate and adaptive immunity.

MacDuff DA, Demorest ZL, Harris RS - Nucleic Acids Res. (2009)

Effect of a nuclear export-defective AID mutant on L1 retrotransposition. (A) Percentage of puromycin-resistant cells that were GFP-positive 5 days after transfection with the L1 and indicated AID variants. A3A and A3AE72A were included as controls. Histogram bars represent the mean of three independent cultures, and the standard deviation is shown. WT, wild-type. (B) Western blot showing expression of the HA-tagged proteins from a representative experiment from (A). Tubulin is a loading control. (C) E. coli-based RifR mutation assay. See the legend to Figure 3C for assay and label details. (D) Localization of GFP-tagged AID and AIDΔC in HeLa cells, in the presence and absence of leptomycin B. The scale bars represent 25 μM.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2665220&req=5

Figure 4: Effect of a nuclear export-defective AID mutant on L1 retrotransposition. (A) Percentage of puromycin-resistant cells that were GFP-positive 5 days after transfection with the L1 and indicated AID variants. A3A and A3AE72A were included as controls. Histogram bars represent the mean of three independent cultures, and the standard deviation is shown. WT, wild-type. (B) Western blot showing expression of the HA-tagged proteins from a representative experiment from (A). Tubulin is a loading control. (C) E. coli-based RifR mutation assay. See the legend to Figure 3C for assay and label details. (D) Localization of GFP-tagged AID and AIDΔC in HeLa cells, in the presence and absence of leptomycin B. The scale bars represent 25 μM.
Mentions: Since L1 undergoes reverse transcription in the nucleus of the host cell, we initially hypothesized that AID would need to be in the nucleus to inhibit this process. However, since mutation of the L1 DNA by AID is not required to inhibit L1 replication, AID could be acting either within the nucleus or within the cytoplasm, where it is localized predominantly [(61); Figure 4D]. To address this question, we tested a variant of AID that is mostly nuclear because it lacks the last 10 amino acids, which includes the nuclear export sequence (AIDΔC) [(62,63); Figure 4D]. AIDΔC inhibited L1 to the same extent as the wild-type protein (Figure 4).Figure 4.

Bottom Line: We found that AID can inhibit the retrotransposition of L1 through a DNA deamination-independent mechanism.This mechanism may manifest in the cytoplasmic compartment co- or posttranslationally.Together with evidence for AID expression in the ovary, our data combined to suggest that AID has innate immune functions in addition to its integral roles in creating antibody diversity.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, Molecular Biology and Biophysics, Institute for Molecular Virology, Center for Genome Engineering, University of Minnesota, Minneapolis, MN 55455, USA.

ABSTRACT
Retrotransposons make up over 40% of the mammalian genome. Some copies are still capable of mobilizing and new insertions promote genetic variation. Several members of the APOBEC3 family of DNA cytosine deaminases function to limit the replication of a variety of retroelements, such as the long-terminal repeat (LTR)-containing MusD and Ty1 elements, and that of the non-LTR retrotransposons, L1 and Alu. However, the APOBEC3 genes are limited to mammalian lineages, whereas retrotransposons are far more widespread. This raises the question of what cellular factors control retroelement transposition in species that lack APOBEC3 genes. A strong phylogenetic case can be made that an ancestral activation-induced deaminase (AID)-like gene duplicated and diverged to root the APOBEC3 lineage in mammals. Therefore, we tested the hypothesis that present-day AID proteins possess anti-retroelement activity. We found that AID can inhibit the retrotransposition of L1 through a DNA deamination-independent mechanism. This mechanism may manifest in the cytoplasmic compartment co- or posttranslationally. Together with evidence for AID expression in the ovary, our data combined to suggest that AID has innate immune functions in addition to its integral roles in creating antibody diversity.

Show MeSH
Related in: MedlinePlus