Alternative splicing and its regulation
Why do human cells express more protein varieties than the genes encoding them? How did this mismatch arise, and is it biologically purposeful? The upshot is that alternative pre-mRNA splicing pathways are responsible for producing molecular decisions in the form of messenger RNA transcripts, which diversify the forms and functions of protein families encoded in the genome. Ultimately, the spliceosome is the biochemical gatekeeper of splicing decisions. It must be nimble in the way it directs decisions about splice site recognition to favor or disfavor one splicing pathway over another, while preserving accuracy. Splicing decisions can have a profound impact on cellular fate and behavior. In the nervous system for example, the inhibition of certain splicing pathways relative to others can automate the time course of differentiation of neuronal precursors into mature cells, whereas other mechanisms specify connectivity patterns and electrical properties of neurons. In many cell types, splicing decisions can indeed have a beneficial effect on protein structure and function, while the elasticity of these pathways offers cells the means to adapt rapidly to local changes in the environment by coordinating their protein outputs.
The Grabowski lab is currently exploring how splicing pathways exhibit elasticity, which is seen by their responsiveness to environmental stimulation and stress. We have developed the Ca2+ permeable NMDA R1 receptor as a model system to understand the biochemistry underlying the elasticity of splicing in neurons, and we are extending our experiments to other model substrates in cancer cells. We are addressing the following set of questions using genetics, biochemistry, and genomics approaches.
Which key players in signaling pathways are activated to respond to environmental cues, and how is target specificity determined?
What is the architecture of splicing codes at the level of pre-mRNA targets, and how do these codes respond to the activated pathways?
How are splicing pathways reset after the external stimulus fades away, and what controls the kinetics of the reset mechanisms?