The CCCTC-binding factor CTCF represses hepatitis B virus Enhancer I and regulates viral transcription by D'Arienzo, V, Ferguson, J, Giraud, G, Chapus, F, Harris, JM, Wing, PA, Claydon, A, Begum, S, Zhuang, X, Balfe, P, Testoni, B, McKeating, JA, Parish, JL