mRNPs: diverse, complex, and utterly fascinating
The success of every organism rests upon proper control of gene expression, and each step in the life cycle of an mRNA provides opportunities for regulation. Rather than existing as naked transcripts, mRNAs are dressed with a variety of protein factors to form mRNA-protein complexes (mRNPs). We are most interested in proteins common to nearly all mRNPs—eIF4E (the cap binding protein), eIF4G (the large scaffold protein) and PABP (the poly(A) binding protein). These three proteins are fundamental for controlling the stability and translatability of a message. Despite a perception that these proteins, especially PABP, are passive participants in the life cycle of an mRNA, it is clear now that the binding of these proteins is tightly regulated and, most importantly, that mRNP organization affects the fate of the transcript.
mRNPs thus represent an important regulatory node for controlling gene expression, yet understanding the relationship between biological processes and mRNP regulation has proven to be challenging. After all, different genes are subject to different post-transcriptional pathways, and, for any specific gene, mRNPs are diverse, transient and dynamic.
Addressing these issues requires a multi-faceted strategy—a reductionist approach to dissect the building blocks of mRNPs, and a holistic approach to characterize emergent properties driven by interactions between these building blocks. Using the powerful combination of classical molecular biology techniques and high-throughput ones to tease apart the large diversity of mRNPs, our goal is to understand the organization and regulation of cytoplasmic mRNPs, and to place mRNP regulation into the contexts of broader biological processes.