Recent study challenges a major tenet of eukaryotic gene expression

Figure 1 Visualisation of ribosomal subunits joining reveal nuclear ribosomes. (A) Model structure of the ribosome tagged with split fragments of yellow fluorescent protein (YFP). (B) Ribosome YFP signal in Drosophila cells, nuclear signal is apparent in a subtype of cells (Type 2). More info in Al-Jubran et al., 2013.

When eukaryotic cells produce new proteins, an elaborate and complex sequence of events is happening in the cell. The DNA, packaged into chromosomes, is partially unpacked, the genetic information stored in the DNA is transcribed to RNA, and finally the protein is synthesized by the ribosome according to the blueprint provided by the RNA.

It has long been accepted among biologists that the processes of transcribing the DNA to RNA and the translation of RNA to the protein happen in two different places of the cell: the former in the nucleus, the latter – after RNA export – in the cytoplasm. There are many good reasons for keeping these two processes separate. One is that the ribosome – the molecular machine synthesizing the protein – might prematurely start reading the RNA, when RNA still needs to be ‘edited’ through a process called splicing. However, recent experiments by Dr Saverio Brogna in the School of Biosciences have shown that at least under certain circumstances the ribosome actually does not wait for the RNA to be exported from the nucleus to the cytoplasm, but gets to the job straight away – in the nucleus. This research was done using the fruit fly Drosophila, an animal model system widely used by geneticists. If proven correct, the finding by Dr. Brogna and his team, published in the journal RNA (Al-Juban et al. RNA, 2013), will require rewriting some chapters of biology text books.

At any rate, it has already made a splash in the blogosphere.