Sp100-HMG drives ‘inside-out’ PML-NB assembly to modulate transcription and cell-cycle dynamics
Bibliographic record
Abstract
Abstract Promyelocytic leukemia nuclear bodies (PML NBs) are membraneless organelles (0.1-1 μ m) integral to fundamental cellular processes, yet the molecular logic governing their hierarchical organization is unclear. Contrary to the classical "PML-sole-scaffold" model, we identify Sp100-HMG as the unique isoform that autonomously nucleates into liquid-like condensates. Our findings establish an "inside-out" assembly paradigm, where Sp100-HMG initiates a liquid core that recruits PML and other client proteins (DAXX, ATRX) through three distinct cooperative processes: I. Multimerization domain- and intrinsically disordered region (IDR)-mediated LLPS of Sp100-HMG, nucleating the core; II. C-terminal-dependent protein-protein interactions enriching client components; and III. SUMOylation-directed PML recruitment, facilitating the formation of a stabilizing peripheral shell. This assembly paradigm extends beyond Sp100-HMG, as evidenced by ZBTB16—a PML NB-associated oncoprotein implicated in acute promyelocytic leukemia — adopting an analogous mechanism to organize PML-positive condensates. Using HEp-2 cells as a main model, we show this hierarchical assembly is critical for orchestrating transcriptional programs and cell-cycle dynamics. Together, our study defines a new biogenesis mode for PML-NBs, where a master liquid nucleator coordinates shell integrity and plasticity for nuclear homeostasis. Significance Statement PML nuclear bodies (PML NBs) serve as essential organizers of the cell nucleus, yet the assembly principles underlying their biogenesis and linking it to functional heterogeneity, spatial positioning, and compositional diversity remain elusive. This study overturns the long-standing "PML-centric" view by establishing an LLPS-driven, hierarchical "inside-out" assembly paradigm. We identify Sp100-HMG as a master liquid nucleator that initiates a core to organize the outer PML shell. This inner-core LLPS-driven assembly logic is shared by other PML NB-associated factors, such as the oncoprotein ZBTB16, providing a unified biophysical framework to explain the structural integrity and plasticity of nuclear condensates. Functionally, this organizational process is critical for shaping the compositional diversity and spatial specificity of PML bodies, thereby modulating transcriptional programs and cell-cycle dynamics in a context-dependent manner. These findings offer broad insights into how organized protein condensation sustains nuclear homeostasis and its dysfunction in diseases such as leukemia.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".