My research interest lies in studying the macromolecular interactions of RNA and proteins in ribonucleoprotein particles (RNPs). RNPs can be very complex and highly versatile molecular machines (e.g. the ribosome, the spliceosome), but to study the underlying principles of RNP activity, I am working with slightly less complex remnants of the ancient RNA world, mobile retroelements.

One of my projects focusses on the self-splicing group II intron ai5γ from S. cerevisiae, which requires high temperature and high salt conditions to self-splice in vitro. In vivo, splicing is dependent on the yeast protein Mss116, but an Mss116 knockout mutant can be rescued by overexpression of the N. crassa protein Cyt-19. Recently it was found that both Mss116 and Cyt-19 enable ai5γ splicing under near-physiological conditions in vitro [1-3]. These proteins belong to the family of DEAD-box proteins, a subset of the Helicase Superfamily 2 (SF2), and they have ATPase and unwinding activities. I am interested in how these proteins assist folding of large multidomain RNA molecules.

My main project involves non-LTR retrotransposons, mobile genetic elements that are evolutionarily related to group II introns. Both classes of elements replicate by a mechanism called target primed reverse transcription (TPRT) [4, 5]. Endonuclease activity in the element-encoded protein initiates the integration process by nicking the target DNA. The generated 3' hydroxyl group serves as primer for reverse transcription of the elements' RNA. Second strand synthesis and complete integration of the new copy occur through variations of host encoded DNA repair. Although this basic concept has been known for more than a decade, many details of TPRT remain unclear. My focus lies in examining the architecture and mode of action of the RNP that initiates and carries out TPRT. I would like to identify the determinants that govern specific recognition between some elements' RNAs and their reverse transcriptase proteins[6, 7], using gel shift essays, CoIP and crosslinking methodologies. Furthermore, retrotransposon reverse transcriptases are an interesting object of study since, unlike most known polymerases, they apparently do not require a primer-template structure to start nucleotide condensation. As this notion is still controversial, I would like to test it by studying the detailed kinetics of TPRT initiation with matched and mismatched substrates.

1. Halls, C., et al., J Mol Biol, 2007. 365(3): p. 835-55.
2. Mohr, S., et al., PNAS, 2006. 103(10): p. 3569-74.
3. Solem, A., Zingler, N., and Pyle, A.M., Mol Cell, 2006. 24(4): p. 611-7.
4. Luan, D.D., et al., Cell, 1993. 72: p. 595-605.
5. Zimmerly, S., et al., Cell, 1995. 82(4): p. 545-54.
6. Osanai, M., et al., Mol Cell Biol, 2004. 24(18): p. 7902-13.
7. Kajikawa, M. and N. Okada, Cell, 2002. 111(3): p. 433-44.