Our lab is interested in the regulation
of complex cellular processes, including
entry into mitosis and apoptosis (programmed
cell death). We are particularly interested
in understanding cellular mechanisms
which prevent the onset of mitosis
prior to the completion of DNA replication
and in the tyrosine kinase signaling
pathways which impinge upon the decision
to apoptose.
To address these problems, we use
cell-free extracts prepared from eggs
of the frog Xenopus laevis which can
recapitulate cell cycle events and
apoptotic processes in vitro.
For the study of cell cycle events,
extracts are prepared which can undergo
multiple rounds of DNA replication
and mitosis in vitro. Progression
through the cell cycle can be monitored
by microscopic observation of nuclear
morphology and by biochemically assaying
the activity of serine/threonine kinases
which control cell cycle transitions.
For the study of apoptosis, modifications
in extract preparation have allowed
us to produce extracts which can apoptotically
fragment nuclei and can accurately
reproduce the biochemical events of
apoptosis, including internucleosomal
DNA cleavage and activation of apoptotic
proteases, the caspases. These powerful in
vitro extracts allow us to examine
and dissect critical signaling events
by:
- immunodepletion of cellular components
from the extracts,
- addition of exogenously produced
recombinant proteins, and
- direct biochemical purification
of regulatory proteins.
Using these molecular
and biochemical approaches, we are working
towards the elucidation of signaling
pathways required for cell proliferation
and cell death.
