A comparison between TR-β gene with mutations in RTH and RARα or PML/RARα genes on the alignment of sequence homology. The mutations in TR-β gene of RTH were clustering almost exclusively in the two regions, I and II, of the hormone binding domain.46 The mutations in the RARα/E-domain of ATRA-resistant APL were indicated as follows: 1, case no. 1; 2, case no. 2; 3 and 5, ATRA-resistant HL-60 subclones^29-31; and 4, a ATRA-resistant NB4 subclone.32