1 Section of Biochemistry, Department of Experimental and Clinical Biomedical Sciences "Mario Serio", University of Florence, Viale GB Morgagni 50, 50134 Florence, Italy. Electronic address: fabrizio.chiti@unifi.it.
2 VIB-KU Leuven Center for Cancer Biology, Herestraat 49 Box 912, 3000 Leuven, Belgium. Electronic address: anna.sablina@kuleuven.be.