GTP Cyclohydrolase 1 Gene 3'-UTR C+243T Variant Predicts Worsening Outcome in Patients with First-Onset Ischemic Stroke

Tetrahydrobiopterin (BH4) is an essential cofactor for all three nitric oxide synthase (NOS isoforms), which plays an important role in vascular diseases. GTP cyclohydrolase 1 (GCH 1) is the first-step and rate-limiting enzyme for BH4 biosynthesis in its de novo pathway. Common GCH1 gene variant C+243T in the 3’-untranslated region predicts NO excretion. The present study examined the predictive role of GCH 1 gene 3’-UTR C+243T variant in the long-term outcome of ischemic stroke. A total of 142 patients with first-onset ischemic stroke were recruited and detected for genotype of GCH1 3’-UTR C+243T by a TaqMan SNP Genotyping assay. Subsequent vascular events and death were de- termined over a 5-year follow-up period. The frequency of GCH1 3’-UTR +243 C/T or T/T genotype was significantly increased in patients with endpoint events as compared with those without events (74% vs 57.8%, P=0.06). Cox regression survival analysis indicated that an increased probability of death or new vascular events was found in patients with GCH1 3’-UTR +243 C/T or T/T genotype com- pared with those with GCH1 3’-UTR C/C genotype (40.6% vs 25.5%), GCH1 3’-UTR +243 C/T or T/T genotype relative to GCH1 3’-UTR C/C genotype was associated with the increased risk of death or vascular events even after adjustment for other risk factors (OR=2.171, 95% CI: 1.066-4.424, P=0.033). It was concluded that GCH1 3’-UTR C+243T variant was an independent predictor of worsening long-term outcomes in patients with first-onset ischemic stroke.

Splicing factor SF3B3,a NS5-binding protein,restricts ZIKV infection by targeting GCH1

Zika virus(ZIKV),a positive-sense single-stranded RNA virus,causes congenital ZIKV syndrome in children and Guillain-Barre Syndrome(GBS)in adults.ZIKV expresses nonstructural protein 5(NS5),a large protein that is essential for viral replication.ZIKV NS5 confers the ability to evade interferon(IFN)signalling;however,the exact mechanism remains unclear.In this study,we employed affinity pull-down and liquid chromatography-tandem mass spectrometry(LC-MS/MS)analyses and found that splicing factor 3b subunit 3(SF3B3)is associated with the NS5-Flag pull-down complex through interaction with NS5.Functional assays showed that SF3B3 overexpression inhibited ZIKV replication by promoting IFN-stimulated gene(ISG)expression whereas silencing of SF3B3 inhibited expression of ISGs to promote ZIKV replication.GTP cyclohydrolase I(GCH1)is the first and ratelimiting enzyme in tetrahydrobiopterin(BH4)biosynthesis.NS5 upregulates the expression of GCH1 during ZIKV infection.And GCH1 marginally promoted ZIKV replication via the IFN pathway.Additionally,GCH1 expression is related to the regulation of SF3B3.Overexpression of the SF3B3 protein effectively reduced GCH1 protein levels,whereas SF3B3 knockdown increased its levels.These findings indicated that ZIKV NS5 binding protein SF3B3 contributed to the host immune response against ZIKV replication by modulating the expression of GCH1.