Coupled Transcription and Translation Within Nuclei of Mammalian Cells

Iborra, Francisco J.
Jackson, Dean A.
Cook, Peter R.

¹Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE UK. ²Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Post Office Box 88, Manchester, M60 1QD UK.

*To whom correspondence should be addressed. E-mail: [email protected]

30 March 2001; accepted 6 June 2001

Published online 21 June 2001; 10.1126/science.1061216

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Science 293(5532):p 1139-1142, August 10, 2001.

It is widely assumed that the vital processes of transcription and translation are spatially separated in eukaryotes and that no translation occurs in nuclei. We localized translation sites by incubating permeabilized mammalian cells with [³H]lysine or lysyl-transfer RNA tagged with biotin or BODIPY; although most nascent polypeptides were cytoplasmic, some were found in discrete nuclear sites known as transcription "factories." Some of this nuclear translation also depends on concurrent transcription by RNA polymerase II. This coupling is simply explained if nuclear ribosomes translate nascent transcripts as those transcripts emerge from still-engaged RNA polymerases, much as they do in bacteria.