Affinage · Plasmodium

PUF2

PF3D7_0417100 · mRNA-binding protein PUF2

Annotated
2026-09-07
12 papers in source corpus 10 papers cited in narrative 10 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PF3D7_0417100 (PfPuf2) is a Pumilio/FBF-family sequence-specific RNA-binding protein that acts as a translational repressor controlling stage-transition decisions in the Plasmodium life cycle (PMID:12409450, PMID:20197405, PMID:23637595). Its Puf domain confers intrinsic, sequence-specific RNA-binding activity, first shown against heterologous Nanos-responsive elements and later against authentic Puf-binding elements (PBEs) in parasite transcripts (PMID:12409450, PMID:23637595). In P. falciparum gametocytes, where the protein is preferentially expressed and cytoplasmically localized, PfPuf2 binds PBEs in both the 5'UTR and 3'UTR of pfs25 mRNA and the 3'UTR of pfs28 to repress their translation, and genetic disruption both de-represses these targets and enhances gametocytogenesis and male-biased sex differentiation, identifying PfPuf2 as a suppressor of sexual commitment (PMID:15585133, PMID:20197405, PMID:23637595). This gametocyte repression operates within a complex containing the stress-granule protein 7-Helix-1, which co-associates with pfs25 mRNA (PMID:30133543). In sporozoites of P. berghei and P. yoelii, the orthologous Puf2 maintains infectious competence and enforces latency during salivary-gland residence: loss of Puf2, or of its RNA-binding domain, causes premature transformation into exo-erythrocytic forms with loss of gliding motility, cell traversal, and infectivity (PMID:21673790, PMID:21625527, PMID:23356439). Mechanistically it acts through translational control of the eIF2α phosphorylation switch, repressing the eIF2α phosphatase transcript uis2 and lying upstream of the eIF2α kinase IK2, and directly binding uis4 mRNA as shown by RNA immunoprecipitation (PMID:21673790, PMID:26808677, PMID:26735921). The protein resides in cytosolic granules distinct from canonical stress granules and P-bodies that dissolve upon hepatocyte infection (PMID:23356439).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2002 Medium

    Establishing whether PfPuf2 is a bona fide RNA-binding protein was the necessary first step; the Puf domain was shown to bind Nanos-responsive elements specifically, defining intrinsic sequence-specific RNA-binding activity.

    Evidence Yeast three-hybrid and in vitro binding assays with bacterially expressed recombinant Puf domain against Drosophila hunchback NRE

    PMID:12409450

    Open questions at the time
    • Binding shown only against a heterologous Drosophila target, not a parasite mRNA
    • No endogenous target identified
    • No cellular localization or stage context
  2. 2004 Medium

    To place PfPuf2 in a life-cycle context, its expression was mapped; the protein is preferentially expressed in gametocyte stages, pointing to a role in sexual-stage biology.

    Evidence Northern blot, Western blot with polyclonal antibodies, RACE/primer extension, and confirmatory yeast three-hybrid binding

    PMID:15585133

    Open questions at the time
    • Function in gametocytes not yet tested
    • Still relies on heterologous NRE target for binding
    • No endogenous mRNA targets
  3. 2010 High

    The functional role of PfPuf2 in gametocytes was resolved genetically: it suppresses gametocytogenesis and male-biased sex differentiation, defining it as a negative regulator of sexual commitment.

    Evidence Endogenous GFP-tagging for cytoplasmic localization, targeted disruption, and episomal complementation with gametocyte quantification in P. falciparum 3D7

    PMID:20197405

    Open questions at the time
    • Direct mRNA targets responsible for the phenotype not identified
    • Mechanism of translational repression not shown
    • No interacting partners
  4. 2011 High

    Whether Puf2 has a role beyond gametocytes was answered in sporozoites: it enforces latency and infectious competence during salivary-gland residence, and lies upstream of the eIF2α kinase IK2.

    Evidence P. berghei puf2- knockout with sporozoite morphology, infectivity, motility and traversal assays, genome-wide transcriptomics, and genetic epistasis with IK2

    PMID:21625527 PMID:21673790

    Open questions at the time
    • Direct Puf2-bound mRNAs in sporozoites not identified
    • How Puf2 regulates IK2 expression unresolved
    • Molecular basis of granule function unknown
  5. 2013 High

    The gametocyte repression mechanism was defined biochemically: PfPuf2 binds PBEs in both 5'UTR and 3'UTR of pfs25 and the pfs28 3'UTR to translationally repress transmission-stage transcripts.

    Evidence In vitro RNA-binding assays plus in vivo de-repression of Pfs25/Pfs28 in PfPuf2-disruptant P. falciparum parasites

    PMID:23637595

    Open questions at the time
    • Full target repertoire beyond pfs25/pfs28 not defined
    • Repression complex composition not characterized
    • 5'UTR PBE mechanism of action unresolved
  6. 2013 High

    The RNA-binding domain was shown to be the functional determinant of sporozoite infectivity, and Puf2 was localized to distinctive cytosolic granules, linking RNA binding to latency granules.

    Evidence P. yoelii knockout with RBD-specific rescue, subcellular localization with stress-granule/P-body marker co-staining, RNA-seq, and oocyst overexpression

    PMID:23356439

    Open questions at the time
    • Composition of the Puf2 granules not defined
    • Direct mRNA targets in these granules not identified in this study
    • Signal triggering granule dissolution unknown
  7. 2016 Medium

    The first direct sporozoite target was identified, closing the gap between phenotype and mechanism: Puf2 binds uis4 mRNA and represses UIS4 protein accumulation.

    Evidence RNA immunoprecipitation from P. berghei salivary-gland sporozoites and UIS4 Western blot in puf2- parasites

    PMID:26808677

    Open questions at the time
    • Single target validated by RIP
    • PBE within uis4 not mapped
    • Direct versus indirect repression not fully separated
  8. 2016 Medium

    Puf2 was connected to the eIF2α phosphorylation switch that gates liver-stage development, by repressing the eIF2α phosphatase transcript uis2 until liver-stage entry.

    Evidence Conditional uis2 knockout and protein-expression analysis with epistasis to the UIS1 kinase pathway in sporozoites

    PMID:26735921

    Open questions at the time
    • Direct Puf2-uis2 binding not demonstrated in this study
    • Mechanism relieving repression at liver-stage entry unknown
    • Species attribution recorded as P. falciparum for a sporozoite phenotype
  9. 2018 Medium

    A physical partner in the gametocyte repression pathway was identified: PfPuf2 forms a complex with the stress-granule protein 7-Helix-1 that co-associates with pfs25 mRNA.

    Evidence Co-immunoprecipitation, mRNA co-immunoprecipitation, and Pfs25 Western blot in 7-Helix-1 knockout female gametocytes

    PMID:30133543

    Open questions at the time
    • Single co-IP without reciprocal validation of the PfPuf2-centered interaction
    • Stoichiometry and additional complex members unknown
    • Whether the complex directly executes translational repression not shown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How Puf2 target selection and repression are relieved to trigger stage transitions — the signals dissolving its granules and switching translational fate at gametocyte commitment and liver-stage entry — remains unresolved.
  • Genome-wide direct target repertoire not defined
  • Molecular composition of Puf2 cytosolic granules unknown
  • Upstream signals controlling repression release uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
7-HELIX-1 (SEVEN-HELIX PROTEIN) [#9]IK2 EIF2Α KINASE (GENETIC, UPSTREAM REGULATION) [#3]UIS2 / UIS2 EIF2Α PHOSPHATASE PATHWAY (GENETIC) [#8]
Complex memberships
PfPuf2–7-Helix-1 complex co-associating with pfs25 mRNA in female gametocytes [#9]

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2002 The Puf domain of PF3D7_0417100 (PfPuf2) binds specifically to the Nanos-responsive elements (NRE) in Drosophila hunchback mRNA, as demonstrated by both the yeast three-hybrid system and in vitro binding assays using recombinant protein expressed in bacteria, establishing intrinsic RNA-binding activity of the PfPuf2 Puf domain. Yeast three-hybrid system; in vitro RNA-binding assay with bacterially expressed recombinant protein Nucleic acids research Medium 12409450
2004 The Puf domain of PF3D7_0417100 (PfPuf2) binds specifically to NRE sequences (Drosophila hunchback mRNA target), confirmed by the yeast three-hybrid system using recombinant PfPuf2 Puf domain, and the protein is preferentially expressed in gametocyte stages as shown by Northern analysis and Western blot with polyclonal antibodies. Yeast three-hybrid system; Northern blot; Western blot with polyclonal antibodies; RNA ligase-mediated RACE and primer extension for transcript mapping DNA and cell biology Medium 15585133
2010 PF3D7_0417100 (PfPuf2) is localized to the cytoplasm of both male and female gametocytes (confirmed by GFP-tagging of the endogenous protein). Targeted disruption of PfPuf2 promotes gametocyte formation and male gametocyte differentiation without affecting asexual growth. Complementation with episomal expression under its cognate promoter partially or fully restored gametocytogenesis rate and sex ratio, confirming PfPuf2 suppresses gametocytogenesis and male-biased sex differentiation. Endogenous GFP-tagging (live imaging); targeted gene disruption; episomal complementation; gametocyte quantification Journal of cell science High 20197405
2011 In P. berghei, PF3D7_0417100 ortholog (Puf2) controls sporozoite latency: in the absence of Puf2, sporozoites in mosquito salivary glands prematurely transform into round forms resembling early intra-hepatic stages and show strong defects in initiating malaria infection in a mammalian host. Puf2 also regulates the expression of the eIF2α kinase IK2 in sporozoites, placing Puf2 upstream of IK2 in the sporozoite latency pathway. Genetic knockout (puf2-); phenotypic analysis of sporozoite morphology and infectivity; genetic epistasis with IK2 PloS one High 21673790
2011 In P. berghei, PF3D7_0417100 ortholog (Puf2) is required to maintain sporozoite infectious competence in mosquito salivary glands; puf2- sporozoites spontaneously initiate exo-erythrocytic form (EEF) development with genome-wide transcriptional changes, loss of gliding motility, loss of cell traversal ability, and reduced infectivity — all occurring independently of normal transmission-associated environmental cues. Genetic knockout; genome-wide transcriptomics; motility assays; cell traversal assays; infectivity assays PLoS pathogens High 21625527
2013 PF3D7_0417100 (PfPuf2) binds to Puf-binding elements (PBEs) located in both the 3'UTR and, for the first time identified, the 5'UTR of the pfs25 mRNA, and also binds to a PBE in the pfs28 3'UTR, mediating translational repression of these transmission-blocking vaccine candidate transcripts in gametocytes. Both in vitro binding assays and in vivo evidence (using PfPuf2 disruptant parasites showing de-repressed Pfs25/Pfs28 expression) confirm this mechanism. In vitro RNA-binding assays; in vivo de-repression in PfPuf2-disruptant parasites; identification of functional 5'UTR PBE in pfs25 PLoS pathogens High 23637595
2013 In P. yoelii, PF3D7_0417100 ortholog (Puf2) maintains sporozoite infectivity during salivary gland residence through its RNA-binding domain (RBD); puf2- sporozoites become progressively non-infectious during prolonged salivary gland residence and prematurely transform into exo-erythrocytic forms. Puf2 localizes to cytosolic granules distinct from stress granules and P-bodies, which disappear rapidly upon hepatocyte infection. Premature overexpression of Puf2 in oocysts deregulates sporozoite maturation and infectivity. Genetic knockout; RNA-binding domain mutant rescue; subcellular localization with marker co-staining; infectivity assays; RNA-seq Cellular microbiology High 23356439
2016 In P. berghei, PF3D7_0417100 ortholog (Puf2) binds to uis4 mRNA in salivary gland sporozoites (demonstrated by RNA immunoprecipitation), and in the absence of Puf2, uis4 mRNA is de-regulated and UIS4 protein is upregulated — establishing uis4 as the first directly identified Puf2-regulated target mRNA in Plasmodium sporozoites. RNA immunoprecipitation (RIP) from salivary gland sporozoites; Western blot for UIS4 protein in puf2- parasites PloS one Medium 26808677
2016 In sporozoites, PF3D7_0417100 ortholog (Puf2) translationally represses uis2 mRNA (encoding the eIF2α phosphatase UIS2); this repression is alleviated when sporozoites develop into liver stages, linking Puf2-mediated translational control to the regulation of the eIF2α phosphorylation/de-phosphorylation switch that governs sporozoite-to-liver-stage transformation. Genetic analysis; protein expression analysis in conditional knockout sporozoites (uis2 cKO); epistasis with UIS1 kinase pathway PLoS pathogens Medium 26735921
2018 PF3D7_0417100 (PfPuf2) forms a complex with the seven-helix protein 7-Helix-1 in P. falciparum female gametocytes, and this complex co-associates with pfs25-coding mRNA. Co-immunoprecipitation established that PfPuf2 and 7-Helix-1 interact physically; gametocytes lacking 7-Helix-1 show impaired Pfs25 synthesis, placing 7-Helix-1 in the same stress granule-based translational repression pathway as PfPuf2. Co-immunoprecipitation; mRNA co-immunoprecipitation; loss-of-function (7-Helix-1 knockout) with Western blot for Pfs25 PLoS pathogens Medium 30133543

Source papers

Stage 0 corpus · 12 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2010 The Puf-family RNA-binding protein PfPuf2 regulates sexual development and sex differentiation in the malaria parasite Plasmodium falciparum. Journal of cell science 78 20197405
2011 Transition of Plasmodium sporozoites into liver stage-like forms is regulated by the RNA binding protein Pumilio. PLoS pathogens 70 21625527
2002 The malaria parasite Plasmodium falciparum encodes members of the Puf RNA-binding protein family with conserved RNA binding activity. Nucleic acids research 67 12409450
2013 Perturbations of Plasmodium Puf2 expression and RNA-seq of Puf2-deficient sporozoites reveal a critical role in maintaining RNA homeostasis and parasite transmissibility. Cellular microbiology 63 23356439
2013 Puf mediates translation repression of transmission-blocking vaccine candidates in malaria parasites. PLoS pathogens 63 23637595
2011 The Puf-family RNA-binding protein Puf2 controls sporozoite conversion to liver stages in the malaria parasite. PloS one 59 21673790
2016 UIS2: A Unique Phosphatase Required for the Development of Plasmodium Liver Stages. PLoS pathogens 38 26735921
2004 Characterization of PfPuf2, member of the Puf family RNA-binding proteins from the malaria parasite Plasmodium falciparum. DNA and cell biology 29 15585133
2018 A seven-helix protein constitutes stress granules crucial for regulating translation during human-to-mosquito transmission of Plasmodium falciparum. PLoS pathogens 22 30133543
2016 Translational Control of UIS4 Protein of the Host-Parasite Interface Is Mediated by the RNA Binding Protein Puf2 in Plasmodium berghei Sporozoites. PloS one 10 26808677
2016 Translational Repression in Malaria Sporozoites. Microbial cell (Graz, Austria) 8 28357358
2026 Molecular mechanisms involved in Plasmodium gametocytogenesis. Frontiers in microbiology 0 41716278