Integration of multiple signals sorts integral inner nuclear membrane (INM) proteins.
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The signals relate to their biogenesis, subcellular traffic and nuclear transport.
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Understanding INM traffic requires consideration of the kinetics in these steps.
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Nuclear transport of membrane and soluble proteins follows common principles in yeast.
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Existence of transport factor mediated nuclear transport in humans is debated.
Past research has yielded valuable insight into the mechanisms that regulate the nuclear transport of soluble molecules like transcription factors and mRNA. Much less is known about the mechanisms responsible for the transportation of membrane proteins to the inner membrane of the nuclear envelope. The key question is: does the facilitated transport of integral inner membrane proteins exist in the same way as it does for soluble proteins and, if so, what is it used for? Herein, we provide an overview of the current knowledge on traffic to the inner nuclear membrane, and make a case that: (a) known sorting signals and molecular mechanisms in membrane protein biogenesis, membrane protein traffic and nuclear transport are also relevant with respect to INM traffic; and (b) the interplay of the effects of these signals and molecular mechanisms is what determines the rates of traffic to the INM.
