- Cyclin H binding to the RARalpha activation function (AF)-2 domain directs phosphorylation of the AF-1 domain by cyclin-dependent kinase 7. Bour, G., Gaillard, E., Bruck, N., Lalevée, S., Plassat, J.L., Busso, D., Samama, J.P., Rochette-Egly, C. Proc. Natl. Acad. Sci. U.S.A. (2005)