title: The timing of pre-mRNA splicing visualized in real-time.
abstract: Since it became clear that intervening sequences or introns are spliced out from precursor pre-mRNA molecules in the nucleus before mature mRNAs are exported to the cytoplasm, questions were raised about the timing of splicing. Does splicing start while RNA polymerase II is still transcribing? Is splicing a slow or a fast process? Is timing important to control the splicing reaction? Although our understanding on the mechanism and function of splicing is largely based on data obtained using biochemical and large-scale "omic" approaches, microscopy has been instrumental to address questions related to timing. Experiments done with the electron microscope paved the way to the discovery of splicing and provided unequivocal evidence that splicing can occur co-transcriptionally. More recently, live-cell microscopy introduced a technical breakthrough that allows real-time visualization of splicing dynamics. We discuss here some of the microscopy advances that provided the basis for the current conceptual view of the splicing process and we outline a most recent development that permits direct measurement, in living cells, of the time it takes to synthesize and excise an intron from individual pre-mRNA molecules.
authors.affiliation: Instituto de Medicina Molecular; Faculdade de Medicina; Universidade de Lisboa; Lisboa, Portugal.
authors.forename: Maria
authors.initials: M
authors.lastname: Carmo-Fonseca
authors.affiliation: Departments of Cell Biology and Pediatrics; Harvard Medical School and Program in Molecular and Cellular Medicine at Boston Children's Hospital; Boston, MA USA.
authors.forename: Tomas
authors.initials: T
authors.lastname: Kirchhausen
mesh_terms: D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D016678:Genome; D007438:Introns; D012322:RNA Precursors / Q000235:genetics* / Q000378:metabolism; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D012322:RNA Precursors; D012333:RNA, Messenger
keywords: RNA; lifetime; live-cell imaging; single-molecule visualization; splicing; transcription