The SAM domain-containing protein 1 (SAMD1) acts as a repressive chromatin regulator at unmethylated CpG islands Por Stielow, B, Zhou, Y, Cao, Y, Simon, C, Pogoda, H-M, Jiang, J, Ren, Y, Phanor, SK, Rohner, I, Nist, A, Stiewe, T, Hammerschmidt, M, Shi, Y, Bulyk, ML, Wang, Z, Liefke, R