Burkitt's lymphoma-associated c-Myc mutations converge on a dramatically altered target gene response and implicate Nol5a/Nop56 in oncogenesis

Burkitt's lymphomas (BLs) acquire consistent point mutations in a conserved domain of Myc, Myc Box I. We report that the enhanced transforming activity of BL-associated Myc mutants can be uncoupled from loss of phosphorylation and increased protein stability. Furthermore, two different BL-associated Myc mutations induced similar gene expression profiles independently of T58 phosphorylation, and these profiles are dramatically different from MycWT. Nol5a/Nop56, which is required for ribosomal RNA methylation, was identified as a gene hyperactivated by the BL-associated Myc mutants. We show that Nol5a is necessary for Myc-induced cell transformation, enhances MycWT-induced cell transformation and increases the size of MycWT-induced tumors. Thus, Nol5a expands the link between Myc-induced regulation of nucleolar target genes, which are rate limiting for cell transformation and tumor growth.