Nucleo-Cytoplasmic Exchange

ID #1218

I just had a question regarding some terminology that I'm mixing up and having a hard time keeping separate. In regards to mature mRNA's being exported from the nucleus, I know that a Nuclear Export Signal needs to be present, but cannot be on the mRNA itself so it's attached to something on the mRNA that is a protein. Does this NES consist of the Nuclear Transport Receptors and exportin combined? What is an "Export Factor" ? I think maybe these are different terms for some of the same things, I'm just confused about what all of these are.

The first thing we need to clear up is that a nuclear export signal (NES) isn't attached to ANYTHING. It's part of the sequence of amino acids in some proteins. Since mRNAs are nucleotides, they can't have amino acid sequences! But a NES is required to get out of the nucleus, so mRNAs aren't going to be able to go by themselves. It just so happens that mRNAs have proteins that "coat" them for a variety of reasons. Since proteins are amino acids, if at least one of these proteins displays an NES, then exportin has something to grab onto. As far as the term "export factor," this is very general terminology that means some molecule associated with the export process.

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