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APOBEC3 proteins inhibit human LINE-1 retrotransposition.
Heide Muckenfuss1, Matthias Hamdorf1, Ulrike Held2
1Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany.
The Journal of Biological Chemistry
|June 1, 2006
Summary
Human APOBEC3 proteins, crucial for innate immunity, can inhibit the retrotransposition of LINE-1 elements by up to 85%. This antiviral defense mechanism appears independent of DNA deamination, highlighting a novel regulatory role for APOBEC3 in controlling mobile genetic elements.
Area of Science:
- Molecular Biology
- Genetics
- Immunology
Background:
- The APOBEC3 (apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3) family comprises human proteins involved in innate defense against retroviruses.
- Long interspersed nuclear elements (LINE-1 or L1s) are mobile genetic elements that can retrotranspose within the human genome.
Purpose of the Study:
- To investigate the impact of APOBEC3 proteins on the retrotransposition of human LINE-1 elements.
- To elucidate the mechanism by which APOBEC3 proteins regulate L1 retrotransposition.
Main Methods:
- Utilized a retrotransposition reporter assay in HeLa cells to quantify L1 transposition frequency.
- Assessed the effect of transiently transfecting various APOBEC3 family members on L1 retrotransposition.
- Employed RNA interference to down-regulate endogenous APOBEC3C expression.
- Performed sequence analyses on L1 elements to identify potential mutational signatures.
Main Results:
- APOBEC3A significantly reduced L1 retrotransposition by up to 85%.
- APOBEC3B, -3C, and -3F inhibited L1 transposition by approximately 75%, while APOBEC3G and -3H showed minimal impact.
- Down-regulation of endogenous APOBEC3C using RNA interference increased L1 retrotransposition by approximately 78%.
- Sequence analysis did not reveal an increased rate of G-to-A transitions, suggesting a DNA deamination-independent mechanism.
Conclusions:
- Host-encoded APOBEC3 proteins play a significant role in regulating LINE-1 retrotransposition.
- The inhibitory activity of APOBEC3 proteins against L1 retrotransposition is not correlated with their nuclear localization.
- The mechanism of L1 inhibition by APOBEC3 proteins appears to be independent of DNA deamination.