tumor suppressor by a yet unknown mechanism (51). Indeed, the heterozygous zebraﬁsh line containing a loss-of-function mutation in one of the two RPL35 alleles has the highest predisposition to cancer among the diﬀerent r-protein genes analysed (51). As previously discussed (17), it seems contradictory that a reduced ribosome synthesis could lead to dysregulation of cell growth and oncogenesis; however, a delayed progression in cell cycle may increase the selective pressure for muta- tions to overcome the problems of a reduced ribosome production. A challenge for future studies will be to elu- cidate the molecular mechanisms underlying the connec- tions between ribosome biogenesis defects and cancer development. SUPPLEMENTARY DATA Supplementary Data are available at NAR Online. ACKNOWLEDGEMENTS The authors dedicate this article to the memory of Dr Marı´ a Rodrı´ guez-Mateos, an excellent scientist and a marvellous person. The authors thank P. Milkereit for communicating results prior to publication, A. D ı´az-Quintana for his in- valuable help with the analysis of the molecular structures and related data and M. Dosil for advice with the GFP-Trap _A procedure. The authors thank D. Kressler and F. Go´ mez-Herreros for critical reading of the manu- script. The authors are indebted to the colleagues men- tioned in the text for their gift of material used in this study. The authors are grateful to M.C. Ruger, M. Rodrı´ guez-Mateos and all members of our and Cha´ vez la- boratory for help and enthusiastic discussions. R.B. is a recipient of a fellowship from the Andalusian Government. FUNDING Spanish Ministry of Science and Innovation and FEDER (BFU2007-60151); Andalusian Government (CVI-271, P07-CVI-02623 and P08-CVI-03508) to J.d.l.C. Funding for open access charge: Spanish Ministry of Science and Innovation and FEDER (BFU2007-60151 to J.d.l.C.). Conﬂict of interest statement. None declared. REFERENCES 1. Steitz,T.A. 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