Our recent investigation in the protist Trichomonas vaginalis suggested a DNA sequence periodicity with a unit length of 120.9 nt, which represents a sequence signature for nucleosome positioning. We now extended our observation in higher eukaryotes and identified a similar periodicity of 175 nt in length in Caenorhabditis elegans. In the process of defining the sequence compositional characteristics, we found that the 10.5-nt periodicity, the sequence signature of DNA double helix, may not be sufficient for cross-nucleosome positioning but provides essential guiding rails to facilitate positioning. We further dissected nucleosome-protected sequences and identified a strong positive purine (AG) gradient from the 5'-end to the 3'-end, and also learnt that the nucleosome-enriched regions are GC-rich as compared to the nucleosome-free sequences as purine content is positively correlated with GC content. Sequence characterization allowed us to develop a hidden Markov model (HMM) algorithm for decoding nucleosome positioning computationally, and based on a set of training data from the fifth chromosome of C. Elegans, our algorithm predicted 60%-70% of the well-positioned nucleosomes, which is 15%-20% higher than random positioning. We concluded that nucleosomes are not randomly positioned on DNA sequences and yet bind to different genome regions with variable stability, well-positioned nucleosomes leave sequence signatures on DNA, and statistical positioning of nucleosomes across genome can be decoded computationally based on these sequence signatures.

Objective 36 non-Kaschin-Beck disease villages in five provinces including Jilin,Liaoning,Shaanxi,Shanxi and Inner Mongolia in the severe endemic areas of Kaschin-Beck disease (KBD) were selected.The aim of this project was to provide the basis showing these KBD villages had already eliminated the KBD.Methods Fully digital versatile X-ray radiography systems (DR) was used to shoot children's right hand X-ray,in accordance with the "Kashin-Beck Disease Diagnosis Standard" (WS/T 207-2010) for diagnosis.Results Results indicated that children showing metaphyseal changes only appeared in 13 of the 36 villages,where the rate of change on metaphyseal was less than or equal to three percent.Conclusion When KBD had been eliminated in a village,the rate of change on aged 7 to 12 children' s metaphyseal would have been less than three percent.