RT Journal Article ID 2e2322cc236bc057 A1 Carmo-Fonseca, Maria A1 Custodio, Noelia A1 Calado, Angelo T1 Intranuclear Trafficking of Messenger RNA JF Critical Reviews™ in Eukaryotic Gene Expression JO CRE YR 1999 FD 1999-12-20 VO 9 IS 3-4 SP 213 OP 219 K1 mRNA transport K1 mRNA surveillance K1 transcriptional termination K1 splicing K1 cleavage and polyadenylation. AB Within the nucleus, protein-encoding genes are transcribed into messenger RNA by RNA polymerase II. Messenger RNAs migrate to the cytoplasm, but before reaching their final destination the primary transcripts must undergo a series of modifications that include 5′-capping, splicing, and 3′-cleavage/polyadenylation. Errors in these processing events can originate aberrant products that, if translated, would produce abnormal proteins. Therefore, it is not surprising that eukaryotes have evolved a surveillance mechanism that recognizes and rapidly degrades aberrant mRNAs. Recent experiments provide exciting insights into how proper mRNAs are distinguished and selected for export. Transcription by RNA polymerase II is directly coupled to pre-mRNA processing, and the mechanism that targets the processing machinery to the polymerase complex suggests a model for co-transcriptional proofreading. Furthermore, there is evidence that at least some mRNAs move randomly throughout the nucleus, presumably by free diffusion. In this light, retention of aberrant mRNAs by the transcription/processing machinery is crucial to prevent their diffusion to the nuclear pores and eventual translocation to the cytoplasm. PB Begell House LK https://www.dl.begellhouse.com/journals/6dbf508d3b17c437,7831059776a36f5d,2e2322cc236bc057.html