Before a cell can build a protein, it first needs a set of 'blueprints', which come in the form of messenger RNA (mRNA). Each mRNA is copied from the corresponding DNA sequence and is then further processed and modified by large multi-protein machines. One of these machines is called cleavage and polyadenylation factor (CPF), which acts at the end of the mRNA. It contains a nuclease enzyme that cleaves the mRNA, and a polymerase enzyme which then adds a poly(A) tail to the freshly-cut end. The cleavage site is often altered in cancer cells and this can affect how the mRNA 'blueprints' are read and can influence mRNA lifetime. But the workings of the CPF machine itself are not well understood. For instance, how is the nuclease correctly positioned and activated only once on every mRNA?
To answer these questions, scientists in Dr Lori Passmore's group at the MRC Laboratory of Molecular Biology deconstructed the machinery and built it up again, piece by piece, until they could replicate the cleavage reactions in a test tube. They also used electron microscopy, X-ray crystallography and mass spectrometry to reveal the molecular architecture of CPF. Together, these combined insights help understand how cleavage sites are determined both in health and disease.
