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. 1999 Jan 5;96(1):5–7. doi: 10.1073/pnas.96.1.5

Figure 1.

Figure 1

Nuclear-cytoplasmic shuttling of the ELAV/Hu protein HuR, which binds to a distinct subset of cellular messenger RNAs. ERG mRNAs encoding protooncoproteins and cytokines are bound to and stabilized by HuR, which contains an amino acid segment (HNS) with both nuclear export and import elements (4). On reaching the cytoplasm, HuR is assumed to release the ERG mRNAs for degradation or translation and may then return to the nucleus (HuR-import) or degrade. Nuclear pores through which mRNPs and proteins may pass are represented as filled circles. The tension between these competing localization signals results in a steady-state distribution of HuR between the nucleus and cytoplasm and may determine the amounts of ERG mRNAs available for translation. ERG mRNAs are assumed to be a subset of the global heterogeneous mRNA population. The hnRNP proteins complexed with ERG mRNAs may contain other nuclear-cytoplasmic shuttling signals (41, 42).