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Updated: Jul 28, 2026

Novel RNA-Binding Proteins Isolation by the RaPID Methodology
Published on: September 30, 2016
Nuclear poly(A)-binding protein PABPN1 is associated with RNA polymerase II during transcription and accompanies the
David G Bear1, Nathalie Fomproix, Teresa Soop
1Department of Cell Biology and Physiology and the UNM Cancer Research and Treatment Center, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA. dbear@salud.unm.edu
Abstract:
The nuclear poly(A)-binding protein, PABPN1, has been previously shown to regulate mRNA poly(A) tail length and to interact with selected proteins involved in mRNA synthesis and trafficking. To further understand the role of PABPN1 in mRNA metabolism, we used cryo-immunoelectron microscopy to determine the fate of PABPN1 at various stages in the assembly and transport of the Chironomus tentans salivary gland Balbiani ring (BR) mRNA ribonucleoprotein (mRNP) complex. PABPN1 is found on BR mRNPs within the nucleoplasm as well as on mRNPs docked at the nuclear pore. Very little PABPN1 is detected on the cytoplasmic side of the nuclear envelope, suggesting that PABPN1 is displaced from mRNPs during or shortly after passage through the nuclear pore. Surprisingly, we also find PABPN1 associated with RNA polymerase II along the chromatin axis of the BR gene. Our results suggest that PABPN1 binds to the polymerase before, at, or shortly after the start of transcription, and that the assembly of PABPN1 onto the poly(A) tail may be coupled to transcription. Furthermore, PABPN1 remains associated with the released BR mRNP until the mRNP is translocated from the nucleus to the cytoplasm.
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