Abstract
RNA-binding proteins are often multifunctional, interact with a variety of protein partners and display complex localizations within cells. Mammalian cytoplasmic poly(A)-binding proteins (PABPs) are multifunctional RNA-binding proteins that regulate multiple aspects of mRNA translation and stability. Although predominantly diffusely cytoplasmic at steady state, they shuttle through the nucleus and can be localized to a variety of cytoplasmic foci, including those associated with mRNA storage and localized translation. Intriguingly, PABP sub-cellular distribution can alter dramatically in response to cellular stress or viral infection, becoming predominantly nuclear and/or being enriched in induced cytoplasmic foci. However, relatively little is known about the mechanisms that govern this distribution/relocalization and in many cases PABP functions within specific sites remain unclear. Here we discuss the emerging evidence with respect to these questions in mammals.
Highlights
Eukaryotic cells rely on post-transcriptional control of gene expression to ensure the tight spatiotemporal control of protein production needed to fulfil their functions
PABP1, the prototypical Poly(A)-binding proteins (PABPs), is diffusely cytoplasmic. Both PABP1 and PABPN1 shuttle between nucleus and cytoplasm making the timing of their exchange on mRNA poly(A) tails unclear, PABPN1 appears required for mRNA export into the cytoplasm [5]
There is no evidence that PABP promotes assembly or disassembly of these granules suggesting that, like in stress granules (SGs), it may accumulate via its association with localized mRNA but this remains to be experimentally verified
Summary
Eukaryotic cells rely on post-transcriptional control of gene expression to ensure the tight spatiotemporal control of protein production needed to fulfil their functions. Their import appears to be via the classical importin β karyopherin receptor pathway, due to importin α, an adaptor protein that binds importin β, interacting with multiple unmapped independent non-canonical NLSs present in the RRMs (RNA-recognition motifs) of PABP1 [11] (Figure 1).
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