Dale A. Ramsden
V(D)J recombination and double strand break repair
V(D)J recombination assembles the immune systems antigen specific receptors by a site-specific DNA rearrangement, termed V(D)J recombination. Only the first step, cleavage of recombination targeting signals by RAG1 and RAG2 proteins, is immune cell specific. In the second step the cleaved DNA ends are joined together using a pathway also employed by all cell types for more general repair of double strand breaks (DSBs). Our lab studes the molecular mechanism of V(D)J recombination and DSB repair, with attention to the role of these processes in development of cancer.
The RAG proteins are capable of an in vitro activity analogous to transposition, the term for the movement of a large family of mobile genetic elements (including retroviruses and LINE elements) in their host genomes. If this in vitro activity were to have a counterpart in cells, it suggests a novel explanation for the relationship between V(D)J recombination and the frequent cancer-causing aberrant rearrangements that occur in immune cells. Our lab is interested in determining the extent to which transposition occurs in cells, as well as how cells might control this process.
We are also studying the function of the different gene products required for end-joining. End-joining is the major pathway for general DSB repair and the only pathway used to resolve V(D)J recombination intermediates. Although genetic analysis has identified a diverse array of factors required for end joining, the molecular functions of these factors are not yet clear. Evidence of interaction between several of the gene products linked to this pathway suggests formation of multi-protein complexes that can perform the end-processing and joining steps appropriate to the structure of different broken ends. We have therefore expressed and purified recombinant versions of these proteins, and will determine how these proteins are assembled into functional end joining complexes, as well as the role of each of these proteins in joining different types of DSBs.