Sequence analysis of the RAR portion of PML/RAR. (A) RT-PCR was performed on total cellular RNA from NB4-R1 cells using a primer in the 3′ UTR of RAR as indicated in this figure. Three independent PCR reactions were performed on the cDNA generated from the RT-PCR reaction. Nested primers were used as indicated in the figure: both inner and outer 5′ primers were in PML and both 3′ primers were in the RAR UTR. The 3′ outer primer was the same as was used for the RT-PCR reaction. (B) Sequence analysis showed a 3-nucleotide deletion: C was deleted from codon 778 and TT from codon 779. This eliminated a phenylalanine but retained a threonine. The reading frame was not disrupted.