The Zn3 Domain of Human Poly(ADP-ribose) Polymerase-1 (PARP-1) Functions in Both DNA-dependent Poly(ADP-ribose) Synthesis Activity and Chromatin Compaction
Bibliographic record
Abstract
PARP-1 is involved in multiple cellular processes, including transcription, DNA repair, and apoptosis. PARP-1 attaches ADP-ribose units to target proteins, including itself as a post-translational modification that can change the biochemical properties of target proteins and mediate recruitment of proteins to sites of poly(ADP-ribose) synthesis. Independent of its catalytic activity, PARP-1 binds to chromatin and promotes compaction affecting RNA polymerase II transcription. PARP-1 has a modular structure composed of six independent domains. Two homologous zinc fingers, Zn1 and Zn2, form the DNA-binding module. Zn1-Zn2 binding to DNA breaks triggers catalytic activity. Recently, we have identified a third zinc binding domain in PARP-1, the Zn3 domain, which is essential for DNA-dependent PARP-1 activity. The crystal structure of the Zn3 domain revealed a novel zinc-ribbon fold and a homodimeric Zn3 structure that formed in the crystal lattice. Structure-guided mutagenesis was used here to investigate the roles of these two features of the Zn3 domain. Our results indicate that the zinc-ribbon fold of the Zn3 domain mediates an interdomain contact crucial to assembly of the DNA-activated conformation of PARP-1. In contrast, residues located at the Zn3 dimer interface are not required for DNA-dependent activation but rather make important contributions to the chromatin compaction activity of PARP-1. Thus, the Zn3 domain has dual roles in regulating the functions of PARP-1. PARP-1 is involved in multiple cellular processes, including transcription, DNA repair, and apoptosis. PARP-1 attaches ADP-ribose units to target proteins, including itself as a post-translational modification that can change the biochemical properties of target proteins and mediate recruitment of proteins to sites of poly(ADP-ribose) synthesis. Independent of its catalytic activity, PARP-1 binds to chromatin and promotes compaction affecting RNA polymerase II transcription. PARP-1 has a modular structure composed of six independent domains. Two homologous zinc fingers, Zn1 and Zn2, form the DNA-binding module. Zn1-Zn2 binding to DNA breaks triggers catalytic activity. Recently, we have identified a third zinc binding domain in PARP-1, the Zn3 domain, which is essential for DNA-dependent PARP-1 activity. The crystal structure of the Zn3 domain revealed a novel zinc-ribbon fold and a homodimeric Zn3 structure that formed in the crystal lattice. Structure-guided mutagenesis was used here to investigate the roles of these two features of the Zn3 domain. Our results indicate that the zinc-ribbon fold of the Zn3 domain mediates an interdomain contact crucial to assembly of the DNA-activated conformation of PARP-1. In contrast, residues located at the Zn3 dimer interface are not required for DNA-dependent activation but rather make important contributions to the chromatin compaction activity of PARP-1. Thus, the Zn3 domain has dual roles in regulating the functions of PARP-1.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 teacher head, 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".