Svend Petersen-Mahrt

Study on the regulation of protein induced DNA deamination

DNA stability is one of the principle elements for survival. Aberrant DNA rearrangement, recombination, or even point mutations can have dire pathogenic consequences. The recent discovery of a family of evolutionary conserved proteins that actively undermine this principle by deaminating dC residues in DNA^1,2,3 has not only lead to the further understanding of the mechanism of immunoglobulin diversification⁴, or identification of a novel means of eliminating viral infection⁵, but also pointed at a new means for the induction of cancer⁶. In the cytoplasm, deamination of dC in DNA due to the APOBEC3 family of proteins seems to solely serve the function of eliminating foreign DNA, including retroviruses. In the nucleus of activated B cells AID introduces dC->dU changes and is responsible for the initiation of DNA mutation (somatic hypermutation) and recombination (class switching and gene conversion) within the immunoglobulin locus⁴.

Understanding the spatial and temporal regulation of these proteins is not only important for the understanding of immune diversification and innate defense, but also with their obvious potential pathogenicity their role in oncogenesis. AID has been know to be B-cell specific since 1999, but the protein itself has not been detected within the nucleus nor has an associated protein been found which would act as a chaperon or a guide for its subcellular location.

The current work would focus on the understanding of the regulation of the subcellular distribution of AID and other family members. For this, classical biochemistry as well as proteomics and immunohistochemistry would be used to study tagged AID in a mutating B cell line. Overlapping with this work would be the analysis of cis-regulatory elements, which determine the exact requirement and potential protein binding sites for immunoglobulin gene diversification.

References

1. Petersen-Mahrt, S. K., Harris, R. S., and Neuberger, M. S. (2002). Nature 418, 99-103.
2. Harris, R. S., Petersen-Mahrt, S. K., and Neuberger, M. S. (2002). Mol Cell 10, 1247-1253.
3. Petersen-Mahrt, S. K., and Neuberger, M. S. (2003). J Biol Chem 278, 19583-19586.
4. Neuberger, M. S., Harris, R. S., Di Noia, J., and Petersen-Mahrt, S. K. (2003). Trends Biochem Sci 28, 305-312.
5. Harris, R. S., Bishop, K. N., Sheehy, A. M., Craig, H. M., Petersen-Mahrt, S. K., Watt, I. N., Neuberger, M. S. and Malim, M. H. (2003). Cell 113, 803-809.
6. Beal, R. C. L., Petersen-Mahrt, S. K., Watt, I., Harris, R. S., Rada, C., and Neuberger, M. S. (2003) (submitted).