Assessment of nucleic acid structure prediction in CASP16
1.This paper presents a comprehensive assessment of RNA and DNA structure prediction in the CASP16 experiment, highlighting the stark contrast in predictive accuracy between nucleic acids and proteins, despite the rise of deep learning models.
2.Blind predictions were submitted for 42 targets by 65 groups from 46 institutions, covering a wide range of systems: RNA and DNA monomers, RNA-only multimers, nucleic acid-protein complexes, and NA-ligand complexes.
3.No prediction of a novel natural RNA structure reached a TM-score above 0.8, indicating that even with recent advances, atomic-resolution prediction of novel RNA structures remains out of reach.
4.Template-based modeling dominated the results: most accurate predictions required a closely related 3D template, and only a few targets, like OLE RNA, were accurately predicted without one—highlighting the dependency on structural homology.
5.Top-performing groups were all human expert teams (Vfold, GuangzhouRNA-human, and KiharaLab), outperforming automated servers like AlphaFold 3, especially for targets with shallow MSAs or no templates.
6.Secondary structure predictions were remarkably strong across the board, even outperforming traditional tools like ViennaRNA or EternaFold, suggesting reliable base-pair information is now extractable from sequence and MSA data alone.
7.However, predictions of pseudoknots, singlet base pairs, and tertiary interactions like A-minor motifs remained inconsistent or poor—critical gaps for enabling accurate 3D folding.
8.In ligand and complex structure predictions, performance was similarly limited unless prior structural templates existed. Complexes with novel binding interfaces were especially challenging.
9.One notable exception was the prediction of the OLE RNA structure, which had no close structural template but deep evolutionary information, suggesting future methods may leverage MSAs better for template-free modeling.
10.The paper introduces a rigorous multi-metric Z-score ranking system to evaluate groups across four categories: monomeric NA, RNA multimers, NA-protein, and NA-ligand complexes.
11.While server models like Yang-Server and AlphaFold 3 improved compared to previous CASPs, they still lagged behind human experts, especially in detecting complex or functionally important motifs.
12.Performance on tertiary motifs such as T-loops, UA-handles, and platforms was mixed, with automated methods performing comparably to humans in some cases, but failing on subtler structural features like intercalated bases.
13.The study advocates for better template identification, enhanced MSA construction, and refined evaluation metrics that go beyond global fold and include functional interaction motifs and quaternary contacts.
14.It also emphasizes the importance of future CASP assessments in benchmarking quaternary structure prediction, including symmetry and stoichiometry inference—areas where predictors still struggle.
15.Overall, CASP16 confirms that nucleic acid structure prediction is advancing, but still lags behind protein structure prediction in accuracy, automation, and reliability—particularly in the absence of experimental or homologous data.
📜Paper:
biorxiv.org/content/10.1101/…
#RNAstructure #DNAbinding #CASP16 #StructuralBiology #ComputationalBiology #RNAfolding #NucleicAcids #DeepLearning #Bioinformatics #RNA3D #AlphaFold