Crossing the borders: poly(A)-binding proteins working on both sides of the fence.
The addition of a 3' poly(A) tail is a pre-requisite for the maturation of the majority of eukaryotic transcripts. In most eukaryotic species, RNA poly(A) tails are bound by two important poly(A)-binding proteins (PABPs): PABPC1 and PABPN1 that localize to the cytoplasm and the nucleus, respectively. Such steady state localization for PABPN1 and PABPC1 led to a model whereby PABPN1-bound nuclear mRNAs are remodeled during or after nuclear export so that PABPN1 is replaced by PABPC1 to allow robust cap-dependent translation in the cytoplasm. Here we discuss evidence that challenge the view in which PABPN1 and PABPC1 function solely in the nucleus and cytoplasm, respectively. We discuss accumulating evidence that support nuclear roles for PABPC1 in mRNA biogenesis as well as cytoplasmic roles for PABPN1 in translational control. Because 3' poly(A) tails can also act as a degradation mark via the exosome complex of 3'-5' exonucleases, we also discuss recent results that involve the nuclear PABP in posttranscriptional gene regulation.
Lemay
Jean-François
JF
Université de Sherbrooke, Department of Biochemistry, Québec, Canada.
Lemieux
Caroline
C
St-André
Olivier
O
Bachand
François
F
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D002451:Cell Compartmentation / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D039122:Poly(A)-Binding Protein I / Q000378:metabolism / Q000502:physiology; D039102:Poly(A)-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology; D012323:RNA Processing, Post-Transcriptional / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism
D039122:Poly(A)-Binding Protein I; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger