DDX5 Antibody

What is DDX5 and why is it significant in research?

DDX5 (also known as p68) is an ATP-dependent RNA helicase and member of the DEAD-box family characterized by a conserved Asp-Glu-Ala-Asp (DEAD) motif. With a molecular weight of approximately 68-70 kDa, DDX5 plays critical roles in:

• Alternative regulation of pre-mRNA splicing

• Transcriptional co-regulation with multiple partners including androgen receptor (AR), p53/TP53, MYOD1, and RUNX2

• miRNA processing

• Cell cycle regulation and proliferation

DDX5 has emerged as a significant research target due to its frequent overexpression in multiple cancers including breast, colon, and prostate cancer .

What applications are DDX5 antibodies validated for?

Based on manufacturer validations and published research, DDX5 antibodies have been successfully used in:

When selecting DDX5 antibodies, researchers should consider the specific application and target species, as reactivity varies between products .

How should DDX5 antibodies be stored and handled?

For optimal performance and longevity:

• Store at -20°C for long-term storage

• Aliquot to prevent repeated freeze-thaw cycles, which can damage antibody quality

• Most commercial DDX5 antibodies are supplied in PBS with 0.02% sodium azide and 50% glycerol at pH 7.3

• Some formulations may contain BSA (0.1%) for additional stability

• Maintain refrigerated at 2-8°C for up to 2 weeks during active use periods

What controls should be included when working with DDX5 antibodies?

When designing experiments with DDX5 antibodies, incorporate these essential controls:

• Positive Controls: Use cell lines with confirmed DDX5 expression such as HeLa, HepG2, NIH/3T3, or MCF-7 cells. Western blot analysis consistently shows DDX5 at approximately 68-70 kDa in these cell lines .

• Knockdown Validation: siRNA-mediated DDX5 knockdown experiments serve as critical specificity controls. For example, siDDX5 design can use sequences such as:

  • siDDX5 #1: 5′-GGUGCAGCAAGUAGCUGCUGAAUAU-3′

  • siDDX5 #2: 5′-GGAAUCUUGAUGAGCUGCCUAAAUU-3′

• Loading Controls: For Western blot applications, use appropriate housekeeping proteins when quantifying DDX5 expression levels.

• Negative Controls: Include normal IgG (matching the host species of your DDX5 antibody) for IP experiments to identify non-specific binding.

How can dilution optimization be performed for different applications?

For robust and reproducible results, optimization of DDX5 antibody dilutions is essential:

Remember that sample-dependent variation may require adjustment of these starting recommendations .

How does DDX5 function in cancer cell proliferation and what experimental approaches best demonstrate this?

DDX5 has been implicated in cancer cell proliferation through multiple mechanisms:

• Cell Cycle Regulation: DDX5 depletion impairs G1-to-S phase progression in various cancer cell lines. Experimental approach:

  • Synchronized cell culture with serum starvation (48h) followed by serum reintroduction

  • Monitor cell cycle progression via flow cytometry after DDX5 knockdown

  • Western blot analysis of cell cycle markers (Cyclins, RB phosphorylation)

  • Results show DDX5-depleted cells progress slower into S-phase than control cells

• Transcriptional Regulation: DDX5 directly regulates DNA replication factor expression by promoting RNA Polymerase II recruitment to E2F-regulated gene promoters. Methodology:

  • Chromatin immunoprecipitation (ChIP) assays targeting DDX5 and RNA Pol II

  • RT-qPCR analysis of E2F target genes following DDX5 knockdown

• Cancer-Specific Dependency: Breast cancer cells with DDX5 gene amplification show heightened sensitivity to DDX5 depletion compared to normal breast epithelial cells. Experimental approach:

  • Compare viability following DDX5 knockdown in cancer cell lines with and without DDX5 amplification

  • Colony formation assays to assess long-term proliferative capacity

How can DDX5's role in acute myeloid leukemia (AML) be studied experimentally?

Research indicates DDX5 plays a crucial role in acute promyelocytic leukemia (APL), a subtype of AML:

• Expression Analysis:

  • Western blot analysis reveals significantly higher DDX5 expression in APL cell lines (NB4 and HL-60) compared to normal neutrophils, PBMCs, and monocytes

  • Quantification shows approximately 3-4 fold higher expression in APL cells

• Functional Studies:

  • siRNA-mediated knockdown of DDX5 or DDX5-targeting antibodies (e.g., 2F5) significantly reduces APL cell viability

  • Cell cycle analysis by flow cytometry demonstrates G0/G1 phase arrest

  • Cell differentiation assessment via CD14 expression shows increased differentiation following DDX5 inhibition

• Mechanism Investigation:

  • ROS (reactive oxygen species) production measurement following DDX5 inhibition

  • Rescue experiments using ROS inhibitors to determine whether effects are ROS-dependent

  • Results indicate DDX5 inhibition promotes APL cell differentiation via induction of ROS

What methodologies are appropriate for studying protein-protein interactions involving DDX5?

DDX5 functions through interactions with multiple protein partners. These can be studied using:

• Co-Immunoprecipitation (Co-IP):

  • Use validated DDX5 antibodies (e.g., 10804-1-AP or 26385-1-AP) for IP at 0.5-4.0 μg per 1-3 mg total protein lysate

  • Include RNase treatment controls to distinguish RNA-dependent from direct protein interactions

  • Western blot analysis of precipitated complexes for known or suspected interaction partners

• Surface Plasmon Resonance (SPR):

  • Can determine binding kinetics and affinity between DDX5 and interaction partners

  • Example protocol: Anti-IgG antibody immobilized on CM5 chip → DDX5 antibody capture → DDX5 protein binding → analyte protein injection

  • Allows quantitative measurement of binding constants (Kd values)

• Proximity Ligation Assay (PLA):

  • In situ detection of protein-protein interactions in fixed cells

  • Particularly valuable for detecting transient or context-dependent interactions

  • Dual antibody approach using DDX5 antibody paired with antibody against suspected interaction partner

Why might DDX5 appear as multiple bands on Western blots?

DDX5 can sometimes appear as multiple bands or at slightly different molecular weights (65-70 kDa) due to:

• Post-translational modifications: DDX5 undergoes phosphorylation, sumoylation, and ubiquitination which can alter its migration pattern

• Alternative splicing: DDX5 exists in multiple isoforms that may be differentially expressed across cell types

• Proteolytic processing: Sample preparation conditions can affect protein integrity

Recommended approach when observing multiple bands:

• Include positive control lysates from well-characterized cell lines (HeLa, HepG2)

• Use fresh protease inhibitors during sample preparation

• Consider phosphatase inhibitors if studying phosphorylated forms

• Validate using knockdown experiments to confirm which bands represent specific DDX5 signals

What are potential challenges when overexpressing DDX5 in experimental systems?

Researchers have reported difficulties in achieving sufficient overexpression of DDX5:

• Tight regulation: DDX5 expression appears to be tightly controlled in cells, making it challenging to achieve substantial overexpression

• Toxicity: High levels of exogenous DDX5 may be toxic to some cell types

• Technical approaches:

  • When attempting RNAi rescue experiments, researchers have observed successful DDX5 transcript overexpression but insufficient protein expression

  • This occurred despite using various expression systems including retroviral transfer and transient transfection with both tagged and untagged constructs

Alternative approaches:

• Use inducible expression systems to achieve controlled expression levels

• Consider cell-specific optimization of transfection conditions

• Employ CRISPR-based approaches for endogenous tagging rather than overexpression

How can antibody specificity between DDX5 and its close homolog DDX17 be ensured?

DDX5 and DDX17 share considerable sequence identity in their helicase core and can interact in cells:

• Antibody selection: Choose antibodies raised against C-terminal regions (amino acids 491-618) where sequence divergence between DDX5 and DDX17 is greatest

• Validation approaches:

  • Perform parallel knockdown experiments targeting DDX5 and DDX17 individually

  • Use recombinant protein controls of both DDX5 and DDX17 on Western blots

  • Cross-validate with multiple antibodies targeting different epitopes

• Mass spectrometry validation: For IP experiments, consider mass spectrometry analysis of immunoprecipitated proteins to confirm specificity

How might DDX5 antibodies be used to identify novel therapeutic targets in cancer?

DDX5 appears to be a promising therapeutic target and diagnostic marker for several cancer types:

• Targeted therapy development:

  • DDX5-targeting therapeutic antibodies (like 2F5) show selective toxicity against APL cells while sparing normal neutrophils

  • DDX5 amplification in breast cancer creates a potential vulnerability that could be exploited therapeutically

  • DDX5 antibodies can be used to screen for small molecule inhibitors of DDX5 function through competition assays

• Biomarker development:

  • IHC analysis of tumor tissues using validated DDX5 antibodies could help stratify patients for targeted therapies

  • Combined analysis of DDX5 and its binding partners may provide more precise prognostic information

• Mechanism investigation:

  • ChIP-seq applications to identify global DDX5 chromatin binding sites

  • RNA-IP to identify DDX5-associated transcripts in different cancer contexts

  • Proteomic analysis of DDX5 interactome in drug-resistant versus sensitive cells

What is known about DDX5's role in RNA metabolism beyond transcriptional regulation?

While DDX5's transcriptional co-regulator function is well-documented, its direct roles in RNA processing require further investigation:

• Pre-mRNA splicing:

  • DDX5's RNA helicase activity increases tau exon 10 inclusion in a RBM4-dependent manner

  • It binds to tau pre-mRNA in the stem-loop region downstream of exon 10

  • Experimental approaches include minigene splicing assays and RNA-protein binding studies

• miRNA processing:

  • DDX5 contributes to miRNA maturation

  • The relationship between DDX5's helicase activity and its role in miRNA biogenesis remains to be fully elucidated

• Circadian rhythm regulation:

  • As a component of the PER complex, DDX5 inhibits 3' transcriptional termination of circadian target genes

  • Further research is needed on how DDX5's enzymatic activities contribute to temporal control of gene expression