Mutational analysis of the 5′ noncoding regions ofBCL-6 in HD cell lines. (A) Analysis by PCR-SSCP. Representative results obtained for PCR products E1.11 and E1.12 are shown. HD cell lines are indicated at the top of each lane by their conventional denomination. A positive control (POS), represented by a tumor sample known to harbor BCL-6 5' mutations, as well as a normal (N) sample, represented by a lymphoblastoid cell line, are also included for each PCR-SSCP fragment shown. Samples were scored positive when their migration pattern differed from the normal control (N) and the migration abnormalities could not be ascribed to population polymorphisms. Among the samples shown, cell lines scored as positive included L-428 for PCR products E1.11 and 1.12 and KM-H2 for PCR product E1.12. (B) Analysis by DNA direct sequencing. The nucleotide sequence of each case shown in the figure is matched to the sequence of a normal control (N) displaying germline BCL-6 alleles. The position of mutations is indicated (arrow) by the nucleotide number of the corresponding BCL-6 germline sequence (the first nucleotide of the BCL-6 cDNA was arbitrarily chosen as position +1).