Mutations in the 3′UTR generate premature polyadenylation signals. Sequencing chromatograms showing premature polyadenylation signals (boxed). (A) Wild-type and mutated cyclin D1a alleles from MCL-tumors 942 and 1176 are shown. The yellow bar highlights the 3 nucleotides at position 1344-46 of wild-type cyclin D1a mRNA that were deleted in MCL-942. In MCL-1176 and Z-138, there was an A insertion before position 1250. (B) The mutated allele of MCL-970 contained a partial duplication (yellow bars), starting at position 1233.