About the Authors
Centro de Biología Molecular ‘Severo Ochoa’ (CSIC-UAM), Cantoblanco, Madrid, Spain
The authors have declared that no competing interests exist.
Conceived and designed the experiments: ÁRO UB. Performed the experiments: APG. Analyzed the data: APG UB. Contributed reagents/materials/analysis tools: DA. Wrote the paper: UB.