NUP145 Antibody

What is NUP145 and why is it important for cellular function?

NUP145 encodes a nucleoporin with a calculated molecular mass of 145.3 kD that belongs to the glycine-leucine-phenylalanine-glycine (GLFG) repeat family of nucleoporins in Saccharomyces cerevisiae. It serves as an essential component of the nuclear pore complex (NPC) and plays critical roles in maintaining nuclear envelope structure and facilitating nucleocytoplasmic transport, particularly in the export of polyadenylated RNAs from the nucleus . Research has demonstrated that disruptions in NUP145 function can lead to severe nuclear envelope abnormalities and defects in mRNA export, highlighting its fundamental importance in cellular compartmentalization and gene expression regulation .

How is NUP145 protein processed in vivo and what are the functions of its resulting domains?

NUP145 is initially synthesized as a precursor protein that undergoes post-translational proteolytic cleavage in vivo. Pulse-chase experiments have revealed that this processing occurs approximately 10 minutes after protein synthesis, yielding two functionally distinct domains: an N-terminal domain (N-Nup145p) of approximately 65 kDa and a C-terminal domain (C-Nup145p) of about 80 kDa . The C-terminal domain (C-Nup145p) is essential for cell viability and integrates into the Nup84p complex, a critical structural component of the NPC. In contrast, while the N-terminal domain (N-Nup145p) is dispensable for cell growth under normal conditions, deletion studies show it contributes to proper NPC distribution and nuclear envelope morphology .

What is known about the structure and composition of complexes containing NUP145?

The C-terminal domain of Nup145p (Nup145p-C) is a core component of the Nup84p complex, which consists of five nucleoporins (Nup84p, Nup85p, Nup120p, Nup145p-C, and Seh1p) and Sec13p, a protein that also functions in COPII vesicle formation . Molecular analysis using quantitative scanning transmission electron microscopy and analytical ultracentrifugation has determined that the Nup84p complex has a molecular mass of approximately 375 kD, consistent with a monomeric complex . Transmission electron microscopy has further revealed that this complex exhibits a distinctive Y-shaped, triskelion-like morphology with a diameter of approximately 25 nm . This architecture is believed to be critical for both NPC biogenesis and nuclear mRNA export processes.

What types of NUP145 antibodies are available and how should researchers select the appropriate one?

When selecting NUP145 antibodies, researchers should consider whether their experimental questions require detection of:

• Full-length precursor protein (145 kDa)

• N-terminal domain specifically (65 kDa)

• C-terminal domain specifically (80 kDa)

• Domain-specific epitopes within either region

Domain-specific antibodies are particularly valuable for distinguishing the localization and functions of each domain. Based on published research protocols, monoclonal antibodies offer high specificity for particular epitopes, while polyclonal antibodies may provide stronger signals by recognizing multiple epitopes . Given that Nup145p undergoes in vivo cleavage within approximately 10 minutes of synthesis, antibodies targeting the full-length precursor may require special timing considerations in experimental protocols .

What are the essential validation steps for NUP145 antibodies?

Proper validation of NUP145 antibodies should include the following steps:

Validation is particularly important when studying NUP145 due to sequence similarities with other GLFG nucleoporins such as Nup116p and Nup100p, which can lead to cross-reactivity issues .

How do strain backgrounds and experimental conditions affect NUP145 antibody performance?

Fixation conditions significantly impact epitope accessibility—formaldehyde fixation (3.7% for 30 minutes) followed by zymolyase treatment (0.5 mg/ml) has been demonstrated to effectively preserve NUP145 epitopes while maintaining nuclear envelope structure in yeast cells . Temperature sensitivity of certain nup145 mutants may necessitate controlled growth conditions prior to antibody applications, as these mutants exhibit distinct phenotypes at restrictive temperatures that can alter antibody binding patterns or protein availability .

What are optimal protocols for immunolocalization of NUP145 in yeast cells?

For successful immunolocalization of NUP145 in yeast cells, researchers should follow this optimized protocol:

• Culture cells to mid-log phase (OD600 ~0.5-0.8)

• Fix cells in 3.7% formaldehyde for 30 minutes at room temperature

• Convert to spheroplasts using 0.5 mg/ml zymolyase 100,000T

• Immobilize spheroplasts on poly-lysine-coated coverslips

• Block non-specific binding with PBS containing 0.2% BSA for 30 minutes

• Apply primary NUP145 antibody (typical dilution 1:100) and incubate for 1-2 hours

• Wash extensively with PBS/BSA buffer

• Apply appropriate secondary antibody (typical dilution 1:100 for FITC or Cy3-conjugated antibodies)

• Counterstain DNA with Hoechst 33258 if desired

• Mount slides and examine using fluorescence microscopy

For co-localization studies with nucleolar markers such as Nop1p, compatible fixation and antibody combinations should be selected, as documented in successful double-labeling experiments .

How can researchers use NUP145 antibodies to investigate nuclear pore complex assembly?

NUP145 antibodies provide powerful tools for investigating NPC assembly through several methodological approaches:

• Time-course analysis during cell cycle: Synchronize cells and collect samples at defined intervals, then use domain-specific antibodies to track the incorporation of N-Nup145p and C-Nup145p into assembling NPCs.

• Pulse-chase immunoprecipitation: Track the maturation of the Nup145p precursor into its cleaved domains during NPC biogenesis using antibodies that recognize epitopes preserved or exposed after cleavage.

• Co-immunoprecipitation studies: Use NUP145 antibodies to isolate complexes at different assembly stages and identify interacting partners through Western blot or mass spectrometry.

• Electron microscopy with immunogold labeling: Precisely localize NUP145 domains within assembling NPCs at nanometer resolution.

• Analysis of mutant phenotypes: Compare NPC assembly patterns between wild-type and various nup145 mutants using immunofluorescence and electron microscopy to identify domain-specific contributions to the assembly process .

The Y-shaped Nup84p complex containing C-Nup145p has been identified as a critical building block in NPC biogenesis, making C-Nup145p-specific antibodies particularly valuable for studying early assembly events .

What are effective approaches for using NUP145 antibodies in protein interaction studies?

To effectively study protein interactions involving NUP145, researchers can employ the following approaches:

• Native co-immunoprecipitation: Using mild lysis conditions (typically Triton X-100-based buffers) and NUP145 antibodies to preserve and isolate intact complexes.

• Tag-based purification with antibody detection: Combining techniques such as ProtA-tagged Nup145p purification with subsequent detection of interacting partners using specific antibodies, as demonstrated in studies identifying interactions between Nup145p and Nup188p .

• Sequential immunoprecipitation: First isolating complexes with anti-NUP145 antibodies, then performing a second immunoprecipitation with antibodies against suspected interaction partners to confirm direct associations.

• Domain-specific interaction mapping: Using antibodies specific to either N-Nup145p or C-Nup145p to determine which domain mediates particular interactions.

• Yeast two-hybrid validation: Confirming interactions identified through antibody-based methods using orthogonal techniques such as yeast two-hybrid assays.

Care must be taken with buffer conditions, as overly stringent detergents may disrupt important but weak interactions within nucleoporin complexes .

How can NUP145 antibodies facilitate studies of nuclear envelope ultrastructure?

NUP145 antibodies have proven instrumental in characterizing nuclear envelope ultrastructure, particularly in mutant analyses. Electron microscopy studies utilizing these antibodies have revealed that deletion/disruption in the amino-terminal half of NUP145 (nup145ΔN) results in dramatic ultrastructural phenotypes, including successive herniations of the nuclear envelope forming grape-like structures at specific sites on the nucleus . These herniations contain numerous NPC-like structures, correlating with the intense patches of anti-nucleoporin immunofluorescence signal observed in light microscopy .

For optimal ultrastructural studies, researchers should:

• Use immunogold labeling with domain-specific NUP145 antibodies to precisely localize protein components within the NPC structure

• Combine thin-section electron microscopy with immunofluorescence to correlate ultrastructural features with protein distributions

• Compare wild-type and mutant strains under identical preparation conditions to identify specific structural roles of different NUP145 domains

• Implement correlative light and electron microscopy approaches to bridge the resolution gap between these techniques

These approaches have revealed that C-Nup145p likely plays a crucial role in anchoring NPCs within the nuclear envelope and maintaining proper spacing between pores .

What methodological considerations are important when studying NUP145 processing and cleavage?

To effectively investigate NUP145 processing and cleavage, researchers should consider these methodological approaches:

• Pulse-chase analysis: The gold standard for studying Nup145p cleavage kinetics involves pulse-labeling with [35S]methionine/cysteine followed by chase with unlabeled amino acids. This approach has revealed that the precursor polypeptide (~145 kDa) is processed within approximately 10 minutes after synthesis .

• Cleavage site mutants: Creating targeted mutations at the evolutionarily conserved cleavage site and monitoring protein processing using antibodies that recognize regions flanking this site.

• Domain-specific antibody selection: Using antibodies that specifically recognize epitopes either N-terminal or C-terminal to the cleavage site to track the fate of each domain.

• Subcellular fractionation: Combining with domain-specific antibodies to determine the localization of cleaved products in different cellular compartments.

• Live-cell imaging: Employing strategically placed fluorescent protein tags and corresponding antibodies for detection in fixed samples to monitor processing dynamics.

Studies using these approaches have demonstrated that cleavage itself is not strictly required for functionality of either domain, suggesting the precursor form may serve primarily to ensure correct targeting or stoichiometric expression of the domains .

How can researchers use NUP145 antibodies to investigate genetic interactions between nucleoporins?

NUP145 antibodies provide powerful tools for investigating genetic interactions between nucleoporins through several sophisticated approaches:

• Analysis of synthetic lethal interactions: In strains with synthetic lethal combinations (such as nup145 with nup116, nup100, or nup188), antibodies can reveal whether lethality correlates with mislocalization of interacting proteins .

• Suppressor screening validation: When genetic suppressors of nup145 mutations are identified, antibodies can determine if suppression occurs through restored localization, altered expression, or compensatory mechanisms.

• Immunoprecipitation in mutant backgrounds: Comparing protein interaction profiles between wild-type and mutant strains can reveal condition-dependent interactions that may explain genetic relationships.

• Complementation analysis with domain-specific antibodies: When expressing individual domains in mutant backgrounds, antibodies can track whether complementation correlates with proper localization of the domain.

• Conditional mutant analysis: Using temperature-sensitive alleles and domain-specific antibodies to track protein localization changes upon shift to restrictive conditions.

These approaches have revealed important genetic relationships, such as the synthetic lethality between strains harboring nup116 mutations and either nup100 or nup145 mutations, suggesting overlapping yet distinct roles for these GLFG nucleoporins .

What are common challenges in NUP145 immunodetection and how can they be addressed?

When troubleshooting immunodetection of NUP145, it's essential to understand that the protein undergoes rapid processing from its precursor form (~145 kDa) to cleaved products (65 kDa N-terminal and 80 kDa C-terminal domains) within approximately 10 minutes of synthesis , which can significantly impact detection outcomes depending on experimental timing.

How should researchers optimize fixation and permeabilization for NUP145 immunofluorescence?

Optimal fixation and permeabilization for NUP145 immunofluorescence requires balancing epitope preservation with accessibility. Based on published protocols, the following approach has proven successful:

• Fixation: Use 3.7% formaldehyde for 30 minutes at room temperature—this concentration and duration have been empirically determined to preserve nuclear envelope structure while maintaining antibody epitopes .

• Spheroplasting: For yeast cells, enzymatic digestion with 0.5 mg/ml zymolyase 100,000T provides appropriate cell wall removal without damaging nuclear structures .

• Cell attachment: Immobilize cells on poly-lysine-coated coverslips to prevent loss during subsequent processing steps.

• Blocking: Include a glycine treatment step (0.2M for 15 minutes) to quench remaining aldehydes before blocking with BSA. This reduces background significantly .

• Antibody penetration: If detecting internal epitopes, gentle detergent treatment (0.1% Triton X-100) may be necessary, but excessive permeabilization can disrupt nuclear envelope structure.

• Buffer conditions: Phosphate buffers (PBS) with controlled ionic strength help maintain antibody specificity while preserving nuclear structure.

For co-localization studies with nucleolar markers such as Nop1p, these conditions have been demonstrated to be compatible with both antibody systems .

What controls and standards should be included in experiments using NUP145 antibodies?

Every experiment utilizing NUP145 antibodies should include the following controls and standards:

• Positive controls:

  • Wild-type cell lysates or fixed cells expressing normal levels of NUP145

  • Recombinant protein domains (when available) for Western blot standards

  • GFP-tagged versions of Nup145p domains when studying localization patterns

• Negative controls:

  • Domain deletion strains (nup145ΔN or nup145ΔC where viable)

  • Secondary antibody-only controls to assess background staining

  • Pre-immune serum controls for polyclonal antibodies

• Specificity controls:

  • Peptide competition assays to confirm epitope-specific binding

  • Cross-reactivity assessment with other GLFG nucleoporins

  • Dilution series to determine optimal antibody concentration

• Technical standards:

  • Molecular weight markers spanning 50-200 kDa range for Western blots

  • Nuclear envelope markers (e.g., Nup49p-GFP) for co-localization studies

  • Loading controls appropriate for subcellular fractionation experiments

• Genetic controls:

  • Complemented deletion strains to confirm phenotype specificity

  • Strains expressing known mutant alleles with characterized phenotypes

These controls are particularly important when working with NUP145 due to its processing into two distinct domains and its structural similarity to other nucleoporins .