PABPN1

PABPN1 is an abundant nuclear protein that binds with high affinity to nascent poly(A) tails. The protein is required for progressive and efficient polymerization of poly(A) tails at the 3' ends of eukaryotic transcripts and controls the size of the poly(A) tail to about 250 nt. At steady-state, this protein is localized in the nucleus whereas a different poly(A) binding protein is localized in the cytoplasm. This gene contains a GCG trinucleotide repeat at the 5' end of the coding region, and expansion of this repeat from the normal 6 copies to 8-13 copies leads to autosomal dominant oculopharyngeal muscular dystrophy (OPMD) disease. Related pseudogenes have been identified on chromosomes 19 and X. Read-through transcription also exists between this gene and the neighboring upstream BCL2-like 2 (BCL2L2) gene.

Poly(A) Binding Protein Nuclear 1

Involved in the 3'-end formation of mRNA precursors (pre-mRNA) by the addition of a poly(A) tail of 200-250 nt to the upstream cleavage product (By similarity).
Stimulates poly(A) polymerase (PAPOLA) conferring processivity on the poly(A) tail elongation reaction and controls also the poly(A) tail length (By similarity).
Increases the affinity of poly(A) polymerase for RNA (By similarity).
Is also present at various stages of mRNA metabolism including nucleocytoplasmic trafficking and nonsense-mediated decay (NMD) of mRNA. Cooperates with SKIP to synergistically activate E-box-mediated transcription through MYOD1 and may regulate the expression of muscle-specific genes (PubMed:11371506).
Binds to poly(A) and to poly(G) with high affinity (By similarity).
May protect the poly(A) tail from degradation (By similarity).
Subunit of the trimeric poly(A) tail exosome targeting (PAXT) complex, a complex that directs a subset of long and polyadenylated poly(A) RNAs for exosomal degradation. The RNA exosome is fundamental for the degradation of RNA in eukaryotic nuclei. Substrate targeting is facilitated by its cofactor MTREX, which links to RNA-binding protein adapters (PubMed:27871484).

Cellular response to lipopolysaccharideISS:UniProtKB
MAPK cascadeISS:UniProtKB
mRNA processingIEA:UniProtKB-KW
Muscle contractionManual Assertion Based On ExperimentTAS:ProtInc
Poly(A)+ mRNA export from nucleusManual Assertion Based On ExperimentIMP:UniProtKB
Positive regulation of polynucleotide adenylyltransferase activityISS:UniProtKB
RNA processingManual Assertion Based On ExperimentTAS:ProtInc

Nucleus
Cytoplasm
Nucleus speckle
Localized in cytoplasmic mRNP granules containing untranslated mRNAs. Shuttles between the nucleus and the cytoplasm but predominantly found in the nucleus (PubMed:10688363).
Its nuclear import may involve the nucleocytoplasmic transport receptor transportin and a RAN-GTP-sensitive import mechanism (By similarity).
Is exported to the cytoplasm by a carrier-mediated pathway that is independent of mRNA traffic. Colocalizes with SKIP and poly(A) RNA in nuclear speckles (By similarity).
Intranuclear filamentous inclusions or 'aggregates' are detected in the myocytes of patients; these inclusions contain PABPN1, ubiquitin, subunits of the proteasome and poly(A) RNA.

Oculopharyngeal muscular dystrophy (OPMD):
A form of late-onset slowly progressive myopathy characterized by eyelid ptosis, dysphagia and, sometimes by other cranial and limb-muscle involvement.

Arginine dimethylation is asymmetric and involves PRMT1 and PRMT3. It does not influence the RNA binding properties (By similarity).