Analysis of PSMB5 gene mutations in bor-tezomib-resistant THP1 cells. Sequencing of PSMB5 gene exon 2 in THP1/WT cells and various BTZ-resistant sublines: THP1/BTZ₇, THP1/BTZ₃₀, THP1/BTZ₁₀₀, and THP1/BTZ_(-100). Depicted is the single nucleotide shift (G→A) at nucleotide position 322 in THP1/BTZ₃₀, THP1/BTZ₁₀₀, and THP1/BTZ_(-100) along with the corresponding change in a single amino acid substitution (Ala49Thr) within the mature PSMB5/β5 protein.