It is not diffusion but rather active transport.Just to make it simple , certain proteins called "export proteins" or ' exportins ' bind to the mRNA (which carries nuclear export signals ) within the nucleus.The exportin protein is also bound to Ran-GTP (compare to ATP for simplicity) .The exportin carries the mRNA to the cytoplasm where Ran-GTP disassociates in to Ran-GDP and mRNA is let free from the exportin protein.
(Original post by ilovemath)
so is post #2 correct - i.e: active transport?
No idea, sorry, we don't go into much detail on the AQA course
However, all Wikipedia mentions, is:
(Original post by Wikipedia Link) Wikipedia Link Another difference between eukaryotes and prokaryotes is mRNA transport. Because eukaryotic transcription and translation is compartmentally separated, eukaryotic mRNAs must be exported from the nucleus to the cytoplasm. Mature mRNAs are recognized by their processed modifications and then exported through the nuclear pore. In neurons, mRNA must be transported from the soma to the dendrites where local translation occurs in response to external stimuli. Many messages are marked with so-called 'zip codes,' which target their transport to a specific location.