通过肽阵列和原生核小体拉下法，鉴定修饰组蛋白作为人类Spindlin家族成员4（SPIN4）的结合底物
2026年3月27日
最近在骨过度生长（一种新型发育障碍）患者中发现了人类Spindlin Family Member 4（SPIN4）中的遗传变异。提出了一种方案和新结果，描述了在核小体背景下对改造组蛋白作为SPIN4结合底物的生化鉴定。
SPIN4是一种调节骨骼发育的组蛋白读取器。SPIN4突变会导致过度生长，但其致病作用尚不明确。该方案可调整并应用于研究组蛋白结合蛋白在所有空间中的结合底物。
首先，将5克牛血清白蛋白（BSA）称重，溶解在100毫升BC-150蛋白储存缓冲液中，准备阻断缓冲液。接下来，用疏水笔勾勒肽阵列上的反应区域，以保护试剂。然后将滤纸放入15厘米的培养皿中，并用水润湿。
将阵列放置在湿润的滤纸上，并小心地在每个阵列区域添加300微升阻断缓冲液。盖好培养皿，在室温下孵化一到三小时。准备一微摩尔重组FLAG标记的Spindlin-4蛋白（或称FLAG SPIN4蛋白）和1个FLAG肽对照组，各自置于阻断缓冲液中。
将试剂和阵列天线转移到冷藏室，以减少背景噪音并提升信噪比。移除数组中多余的阻塞缓冲区。在每个块上加入FLAG SPIN4蛋白，或称FLAG肽对照。
盖好培养皿，准备在冷藏室过夜孵化。在洗衣盒中加入50毫升肽阵洗缓冲液。将蛋白质溶液从阵列中丢弃，并以反应面朝上转移到洗涤缓冲液中。
把阵法洗五遍。前两次洗涤各一分钟，随后进行三次各五分钟的洗涤。然后用阻断液冲洗，去除残留的洗涤剂。
把这些阵列放回培养皿。每个块块加入300微升抗FLAG抗体，并在室温下培养一小时。丢弃抗体溶液，将阵列转移到洗涤缓冲液中，并按照之前演示重复洗涤。
每个块块加入300微升HRP结合山羊抗小鼠IgG IgG二级抗体溶液，并在室温下培养一小时。丢弃抗体溶液，并按照之前演示的步骤清洗阵列五次。将阵列放入透明保护膜内，加入一毫升增强型化学发光（ECL基底），确保覆盖均匀。
清除被困的气泡。使用数字成像仪捕捉明场图像中的化学发光。将原始数据文件上传到MODified组肽阵列分析软件后，在“点比对”标签页中确认每个网格都以肽点为中心。
在“点点统计”中，检查重复点相关系，确保误差小于5%。使用反应性标签评估不同组蛋白修饰间的结合。然后使用特异性标签确定目标肽在不同组蛋白修饰中的相对结合偏好。制备2倍珠阻缓冲液时，将1克BSA加入10毫升BC-150裂解缓冲液中，并用漩涡溶解。
将含有等摩尔浓度的FLAG SPIN4和FLAG SPIN4 D82H突变珠转移到分别的1.5毫升管中。在野生型样本中加入等量的100毫莫拉1X FLAG肽负对照珠。使用适当量的BC-150溶解缓冲液将所有样品均匀调整到均匀体积。
在每根管子上加入等量的2X珠阻缓冲液，使最终体积达到一毫升。在设定为4摄氏度、20转/分钟的管状旋转器上孵育一夜。为了启动核小体结合，将从HEK293FT细胞中提取的1X单核小体解冻在冰上。
为初步优化，计算1X核小体与SPIN4蛋白的1比1摩尔比值。将1X核小体与2X小珠阻断缓冲液等量混合。然后将混合物与预先堵塞的珠子混合在15毫升管中，在管子旋转器上以4摄氏度、20转/分钟的温度孵育4小时进行复合。
在3000克下离心，温度为四摄氏度，离心三分钟。丢弃上清液后，将珠子重新悬浮于一毫升BC-150溶解缓冲液中，转移到1.5毫升的管子中。要洗三次珠子，用3000克离心机加热一分钟。
丢弃上清液后，将沉淀液重新悬浮于一毫升BC-150溶解缓冲液中。偶尔搅动管子，使珠子均匀分布于重复洗涤之间。然后进行两次额外洗涤，在休养和离心之间，在旋转器上以20转/分钟、摄氏4度的10分钟孵育步骤。
最终清洗后，将珠子重新悬浮在九柱的BC-150溶解缓冲液中。将每个样品中的160微升珠子与40微升5X Laemmli缓冲液混合。加热95摄氏度五分钟以实现变性。
可选地，为了获得更干净且背景更少的结果，可以对蛋白质核小体复合体进行FLAG肽错觉。在室温下用3000克离心机离心五分钟。然后进行银染色和西方墨迹法，以验证和检测修正组蛋白SPIN4结合。
SPIN4显著结合组蛋白H3赖氨酸4（H3K4）、单甲基、二甲基和三甲基肽。相反，SPIN4 D82H功能丧失突变体对所有靶点的结合减少，证实都铎结构域1对底物结合至关重要。SPIN4的结合亲和力受到其他翻译后修饰的负面影响，这些都必须确认，如H3R2me2s和H3R2me2a。
通过一致的肽阵列观察，SPIN4 D82H相较野生型SPIN4显示出整体核小体结合的减少。对SPIN4和SPIN4 D82H的拉下样本进行Western blot分析，进一步显示SPIN4 D82H与单甲基、二甲基或三甲基H3K4肽无定量结合，验证了这些快速识别相关组蛋白翻译修饰底物的双重方法。快速且有针对性的组蛋白结合底物验证。
每个候选组蛋白的表达和纯化条件可能有所不同。在天然单核小体拉下后进行组蛋白质谱分析，将全面了解组蛋白PTM的范围。
查看完整文字稿并访问数千部科学视频
Overview
This article presents a protocol for identifying the binding substrates of human Spindlin Family Member 4 (SPIN4), a histone reader implicated in bone growth regulation. The study details the use of peptide arrays and nucleosome pulldown assays to characterize the binding specificity of wild-type and mutant SPIN4, providing insights into its role as an epigenetic reader and its involvement in overgrowth syndromes.
Key Study Components
Area of Science
- Epigenetics
- Protein biochemistry
- Bone biology
Background
- SPIN4 is a histone reader protein involved in bone development.
- Loss-of-function mutations in SPIN4 are linked to pre- and post-natal overgrowth syndromes with X-linked dominant inheritance.
- SPIN4 contains three Tudor domains, which are potential epigenetic reader domains for methylated histone residues.
- The precise binding substrates and functional mechanisms of SPIN4 were previously unclear.
Purpose of Study
- To identify and validate the histone binding substrates of SPIN4.
- To compare the binding affinities of wild-type and disease-associated mutant SPIN4.
- To establish a rapid protocol for substrate identification of histone-binding proteins.
Methods Used
- Expression and purification of recombinant FLAG-tagged SPIN4 (wild-type and D82H mutant) using an insect cell system.
- Histone modification peptide array to assess binding specificity and affinity.
- Biochemical pulldown assays using native mononucleosomes extracted from HEK293FT cells.
- Silver staining and Western blotting to validate histone binding.
- Data analysis using MODified Histone Peptide Array Analysis software.
Main Results
- Wild-type SPIN4 binds specifically to histone H3 lysine 4 (H3K4) mono-, di-, and trimethylated peptides.
- The D82H loss-of-function mutant exhibits significantly reduced binding to all H3K4 methylation states, indicating the importance of Tudor domain 1.
- SPIN4 binding is negatively affected by additional post-translational modifications such as H3R2me2s and H3R2me2a.
- Western blot and peptide array results consistently show diminished nucleosome binding by the mutant compared to wild-type SPIN4.
Conclusions
- SPIN4 is a bona fide reader of H3K4 methylation marks.
- The D82H mutation disrupts SPIN4's substrate binding, highlighting the functional significance of Tudor domain 1.
- This protocol enables rapid and targeted identification of histone-binding protein substrates and can be adapted for other candidates.
Frequently Asked Questions
Executive Industry Relevance
Rapid identification of histone-binding substrates for epigenetic reader proteins like SPIN4 is critical for de-risking early discovery and clarifying target mechanisms in chromatin biology. This protocol enables quantitative assessment of binding specificity and functional validation, supporting predictive confidence in target validation and mechanistic studies. The approach is directly relevant for portfolio triage and prioritization of epigenetic targets in preclinical pipelines.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables interrogation of epigenetic reader protein substrate specificity for mechanistic de-risking.
- Supports functional target validation by distinguishing wild-type from loss-of-function variants.
- Provides quantitative binding data to inform predictive confidence in target selection.
Screening & Assay Development
- Facilitates preparation of validated peptide arrays and nucleosome pulldown assays for downstream workflows.
- Delivers standardized, reproducible, and quantitative readouts for assay development.
- Enables reliable evaluation of compound or variant effects on histone binding.
Translational & Preclinical Research
- Aligns substrate identification with disease-relevant epigenetic mechanisms for translational continuity.
- Supports risk-adjusted advancement decisions by clarifying functional consequences of mutations.
- Provides a platform for biomarker alignment in chromatin-modifying target programs.
Pipeline & Workflow Integration
This method integrates into the discovery continuum from early target validation through assay development and preclinical mechanistic studies.
- Discovery Biology: Supports hypothesis testing and pathway clarification for epigenetic reader proteins.
- Screening: Provides assay-ready, quantitative, and reproducible binding data for screening campaigns.
- Analytics: Delivers statistical outputs and comparative measurements for variant and condition assessment.
- Translational Research: Connects substrate specificity to disease-relevant chromatin states when supported by functional data.
- Enterprise Reuse: Offers a reusable protocol adaptable to other histone-binding protein targets.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence and reduces mechanistic ambiguity in epigenetic target validation.
- Operational Value: Standardizes substrate identification and enables reproducible, scalable workflows.
- Strategic Value: Improves go/no-go decisions and capital efficiency by clarifying target engagement.
- Portfolio Impact: Supports risk-adjusted prioritization and advancement of chromatin-modifying targets.
Implementation Considerations
- Requires expertise in protein expression, peptide array handling, and chromatin biochemistry.
- Needs access to digital imaging, peptide array analysis software, and Western blot infrastructure.
- Demands cross-team standardization for data analysis and interpretation.
- Adaptation may be necessary for different histone-binding proteins or model systems.
- Expression and purification conditions may vary for each candidate protein, impacting throughput.
