Affinage

PAPOLA

Poly(A) polymerase alpha · UniProt P51003

Length
745 aa
Mass
82.8 kDa
Annotated
2026-06-10
14 papers in source corpus 4 papers cited in narrative 4 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PAPOLA encodes poly(A) polymerase α, a template-independent nucleotidyltransferase that adds poly(A) tails to mRNA 3' ends and thereby governs both bulk RNA maturation and the regulated translational control of specific transcripts (PMID:34048556, PMID:39617768). In maturing mouse oocytes, PAPOLA drives cytoplasmic polyadenylation of maternal mRNAs required for meiotic cell-cycle progression: it localizes to the germinal vesicle and redistributes to the ooplasm after germinal vesicle breakdown, and upon meiotic resumption CDK1 and ERK1/2 cooperatively phosphorylate it at S537, S545, and S558 to boost its activity, enabling translational activation even of transcripts lacking canonical cytoplasmic polyadenylation elements; activated PAPOLA further stimulates polyadenylation and translation of its own Papola mRNA in a 3'-UTR-dependent positive feedback loop (PMID:34048556). In somatic cells PAPOLA controls alternative polyadenylation and 3'-UTR length of target mRNAs such as CCND1, with its level dictating 3'-UTR shortening, steady-state transcript abundance, and proliferative/anchorage-independent growth (PMID:33712453). PAPOLA also acts redundantly with TENT2 and PAPOLG as a backup adenylation pathway for unadenylated premature transcription termination products when the NEXT-mediated degradation route is compromised (PMID:39617768). Its own expression is constrained at the translational level by a conserved 5'-proximal upstream ORF that represses translation of the downstream coding sequence (PMID:20174964).

Mechanistic history

Synthesis pass · year-by-year structured walk · 4 steps
  1. 2010 Medium

    Established that PAPOLA's own synthesis is translationally constrained, identifying a built-in autoregulatory brake on poly(A) polymerase levels.

    Evidence 5'-UTR/transcription start mapping and uORF AUG mutagenesis with translational efficiency reporters

    PMID:20174964

    Open questions at the time
    • Does not link uORF-mediated repression to any physiological condition or signal
    • Mechanism of uORF re-initiation/bypass not defined
    • No connection to PAPOLA enzymatic output established
  2. 2021 High

    Defined PAPOLA as the enzyme driving cytoplasmic polyadenylation during oocyte meiosis and revealed CDK1/ERK1/2 phosphorylation as the switch that upregulates its activity and triggers an autocatalytic feedback loop.

    Evidence Localization imaging, activity inhibition with meiotic-arrest readout, phosphosite mutagenesis, kinase assays, and polyadenylation/translation reporters in mouse oocytes

    PMID:34048556

    Open questions at the time
    • Full set of maternal mRNA targets not enumerated
    • Mechanism by which phosphorylated PAPOLA acts on CPE-lacking transcripts unresolved
    • Structural basis of phosphoregulation at S537/S545/S558 unknown
  3. 2021 Medium

    Showed PAPOLA controls alternative polyadenylation in somatic cells, linking its level to CCND1 3'-UTR length, mRNA abundance, and cancer cell proliferation.

    Evidence siRNA knockdown and overexpression in breast cancer cells with CCND1 3'-UTR/poly(A) analysis, Western blot, and proliferation/soft-agar assays

    PMID:33712453

    Open questions at the time
    • How PAPOLA biases poly(A) site choice mechanistically is not defined
    • Genome-wide APA targets beyond CCND1 not mapped
    • Whether phosphoregulation operates in this somatic context untested
  4. 2024 Medium

    Placed PAPOLA in a redundant backup adenylation pathway acting on premature transcription products, defining a fail-safe role when NEXT-mediated nuclear surveillance is lost.

    Evidence NEXT inactivation with RNA 3'-end sequencing, depletion of TENT2/PAPOLA/PAPOLG, and global translation/viability assays

    PMID:39617768

    Open questions at the time
    • Relative contribution of PAPOLA versus TENT2/PAPOLG not quantified
    • Substrate selectivity that distinguishes backup from canonical adenylation unknown
    • Whether this role occurs under physiological (non-perturbed) conditions unclear

Open questions

Synthesis pass · forward-looking unresolved questions
  • How PAPOLA substrate selection and activity are coordinated across its nuclear canonical, cytoplasmic CPE-independent, alternative-polyadenylation, and surveillance-backup roles remains unresolved.
  • No unifying model linking phosphoregulation to target choice across contexts
  • No structural data on the active enzyme in these timeline studies
  • Interplay with cofactors directing nuclear versus cytoplasmic activity uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140098 catalytic activity, acting on RNA 3 GO:0016740 transferase activity 2
Localization
GO:0005634 nucleus 1 GO:0005829 cytosol 1
Pathway
R-HSA-8953854 Metabolism of RNA 3

Evidence

Reading pass · 4 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2021 PAPα (PAPOLA) is the poly(A) polymerase that catalyzes cytoplasmic mRNA polyadenylation during mouse oocyte maturation. PAPα localizes to the germinal vesicle (GV) in fully grown oocytes and redistributes to the ooplasm after GV breakdown. Inhibition of PAPα activity impairs cytoplasmic polyadenylation and translation of maternal transcripts, blocking meiotic cell cycle progression. Upon meiosis resumption, CDK1 and ERK1/2 cooperatively phosphorylate three serine residues (S537, S545, S558) of PAPα, increasing its activity and enabling translational activation of transcripts lacking cytoplasmic polyadenylation elements in their 3'-UTR. Activated PAPα then stimulates polyadenylation and translation of its own Papola mRNA via a positive feedback circuit in a 3'-UTR polyadenylation signal-dependent manner. Live cell imaging (localization), inhibition of PAPα activity with phenotypic readout (meiotic arrest), phosphorylation site mutagenesis, CDK1/ERK1/2 kinase assays, polyadenylation assays, translational reporters Nucleic acids research High 34048556
2021 PAPOLA silencing in breast cancer cells (MCF-7, MDA-MB-231) reduces cyclin D1 (CCND1) mRNA and protein levels and reduces proliferation and anchorage-independent growth. Silencing PAPOLA lengthens the CCND1 mRNA 3'-UTR (without changing poly(A) tail length), while PAPOLA overexpression causes CCND1 mRNA 3'-UTR shortening and increased CCND1 transcript and protein levels. These data establish PAPOLA as a regulator of CCND1 alternative polyadenylation that influences 3'-UTR length and steady-state mRNA levels. siRNA knockdown, PAPOLA overexpression, qRT-PCR for CCND1 mRNA and poly(A) tail length, 3'-UTR analysis, Western blot for CCND1 protein, proliferation and soft agar anchorage-independent growth assays Journal of cell science Medium 33712453
2010 The PAPOLA mRNA contains a 211-bp GC-rich 5'-UTR with two upstream open reading frames (uORFs) conserved across species. Mutation of the 5'-proximal AUG increased translational efficiency of the downstream coding sequence, while mutation of the second AUG had no significant effect, establishing that the first uORF acts as a translational repressor of PAPOLA expression. 5'-UTR mapping (transcription start site determination), uORF identification, uORF AUG mutagenesis with translational efficiency assays Molecular and cellular biochemistry Medium 20174964
2024 Upon inactivation of the Nuclear EXosome Targeting (NEXT) complex, longer unadenylated premature transcription termination products are redundantly adenylated by TENT2, PAPOLA, and PAPOLG as a backup pathway. These adenylated transcripts are then degraded via the nuclear PAXT connection or exported and removed by the cytoplasmic exosome in a translation-dependent manner; failure to remove them decreases global translation and induces cell death. NEXT complex inactivation, RNA 3'-end sequencing, genetic depletion of tailing enzymes (TENT2, PAPOLA, PAPOLG), measurement of global translation, cell viability assays Nature communications Medium 39617768

Source papers

Stage 0 corpus · 14 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2016 Long-Term Transcriptomic Effects of Prebiotics and Synbiotics Delivered In Ovo in Broiler Chickens. PloS one 45 28002487
2013 Nuclear transfer technique affects mRNA abundance, developmental competence and cell fate of the reconstituted sheep oocytes. Reproduction (Cambridge, England) 34 23401598
2021 Oocyte meiosis-coupled poly(A) polymerase α phosphorylation and activation trigger maternal mRNA translation in mice. Nucleic acids research 23 34048556
2019 Inhibition of Skp1-Cullin-F-box complexes during bovine oocyte maturation and preimplantation development leads to delayed development of embryos†. Biology of reproduction 21 30535233
2021 PAPOLA contributes to cyclin D1 mRNA alternative polyadenylation and promotes breast cancer cell proliferation. Journal of cell science 12 33712453
2022 Oocyte quality and in vivo embryo survival after ovarian stimulation in nulliparous and multiparous rabbit does. Theriogenology 8 35724452
2020 Hypereosinophilic Syndrome, Multiorgan Involvement and Response to Imatinib. Cureus 5 32656011
2010 The structure of the 5'-untranslated region of mammalian poly(A) polymerase-alpha mRNA suggests a mechanism of translational regulation. Molecular and cellular biochemistry 4 20174964
2024 RNA 3'end tailing safeguards cells against products of pervasive transcription termination. Nature communications 2 39617768
2020 Prenatal diagnosis and molecular cytogenetic characterization of a de novo 3.19-Mb chromosome 14q32.13-q32.2 deletion of paternal origin. Taiwanese journal of obstetrics & gynecology 1 32917334
2016 Polyadenylated tail length variation pattern in ultra-rapid vitrified bovine oocytes. Veterinary world 1 27847415
2026 Torpor-Induced Regulation of Poly(A) Tail Machinery in 13-Lined Ground Squirrel Brown Adipose Tissue. Journal of developmental biology 0 42201243
2025 Development and Validation of the FIP Score for the Screening of FIP1L1::PDGFRA-Associated Hypereosinophilic Syndrome. The journal of allergy and clinical immunology. In practice 0 40992688
2024 Cross-disease transcriptomic analysis reveals DOK3 and PAPOLA as therapeutic targets for neuroinflammatory and tumorigenic processes. Frontiers in immunology 0 39726593

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