The biochemistry of RNA metabolism studied in situ.

In vitro assays have contributed important insights into the mechanisms of RNA metabolism in cells. A growing collection of microscopy techniques is allowing the measurement of macromolecular binding and complex formation in the context of a real cell. We will first discuss two of the more established techniques. Fluorescence resonance energy transfer (FRET) identifies binding partners, pairs of molecules residing in the same macromolecular complexes. The complimentary technique of fluorescence recovery after photobleaching (FRAP) measures the rates of binding and unbinding of those molecules in their complexes. A newer technique--in vitro FRAP--assesses the regulation of binding and complex formation by co-factors in the nucleus.