Fig. 6

B4GALT1 regulates TAZ glycosylation to promote PD-L1 transcription. A Analysis of luciferase activity in A549 cells transfected with a full-length CD274 promoter and a B4GALT1 overexpression plasmid. The results are expressed as the fold change compared with the control cells. B, C A549 cells with TAZ knockdown and PD-L1 expression were analysed by qRT‒PCR and western blotting. D Analysis of the luciferase activity of CD274 in A549 cells transfected with a full-length CD274 promoter construct or a construct with deletion of the -101 to -39 CD274 promoter region and knockdown of TAZ. The results are expressed as fold changes compared with the control cells. E Analysis of the luciferase activity of CD274 in A549 cells transfected with the CD274 promoter construct with deletion of the -101 to -39 region and a B4GALT1 overexpression plasmid. The results are expressed as fold changes compared with the control cells. F Analysis of the luciferase activity of CD274 in A549 cells transfected with the full-length CD274 promoter construct, along with B4GALT1 pcDNA or TAZ siRNA. The results are expressed as fold changes compared with the vector cells. G, H qRT‒PCR and western blot analyses revealed that TAZ knockdown mitigated the B4GALT1-induced upregulation of PD-L1 mRNA and protein levels. I, J A549 cells were transfected with si-B4GALT1 or pcDNA-B4GALT1, and TAZ expression was analysed by qRT‒PCR and western blotting. K Western blot analysis of TAZ expression in A549 cells with or without B4GALT1 knockdown or overexpression followed by treatment with CHX. L Coimmunoprecipitation experiments indicated that B4GALT1 interacted with TAZ in A549 cells. M Detection of TAZ bound to GST-B4GALT1 or GST in a GST pull-down assay. N Western blot analysis of TAZ levels in B4GALT1 knockdown cells, B4GALT1-overexpressing cells, and tunicamycin (TM)-treated cells. *P < 0.05, **P < 0.01, n.s., not significant. O Western blot analysis of Flag-tagged WT or mutated TAZ expression levels in B4GALT1-overexpressing A549 cells followed by treatment with CHX