Gene expression in eukaryotic cells
I conservatively counted 24 recently discovered mechanisms that help regulate gene expression in eukaryotic cells, as reviewed by Moore and Proudfoot.1 Here are just a few of them.
Chromatin is not loosely wadded DNA inside cellular nuclei. Instead, it is very precisely organized, with specific portions dynamically looped outward. Each loop is associated with a separate nuclear pore, and can retract to a storage position when appropriate. Robust and efficient machinery ensures that the correct portions of chromatin are unspooled from nearer the center of the nucleus to an appropriate nuclear pore. Each pore is extremely active, with a host of interacting regulatory RNA’s, proteins, and ribonucleoproteins.2 These send and receive communications from and toward the farthest ends of the RNA and protein manufacturing processes.
RNA Polymerase does not typically transcribe DNA in fluid space, but is attached to a cadre of proteins associated with each nuclear pore. This way, the rapidly emerging RNA transcript is already proximal to the pore, through which much of it will exit to the cytoplasm. Further, cell biologists have determined that the first copy of a transcript is like a practice run. This first, rough draft RNA transcript either serves as a quality control run, so that its integrity is ensured prior to full manufacture and export from the nucleus, as a primer for the total set of transcript processing machinery to be properly set, as a chemical communicator providing information to downstream processes, or all three….
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