Aminoglycosides are efficient reagents to induce readthrough of premature termination codon in mutant B4GALNT1 genes found in families of hereditary spastic paraplegia

2020 ◽  
Vol 168 (2) ◽  
pp. 103-112 ◽  
Author(s):  
Farhana Yesmin ◽  
Robiul H Bhuiyan ◽  
Yuhsuke Ohmi ◽  
Yuki Ohkawa ◽  
Orie Tajima ◽  
...  
Keyword(s):  
Hereditary Spastic Paraplegia ◽  
Premature Termination ◽  
Premature Termination Codon ◽  
Full Length ◽  
Termination Codon ◽  
Dependent Manner ◽  
Spastic Paraplegia ◽  
Before And After ◽  
Faint Band ◽  
First Time

Abstract The readthrough of premature termination codon (PTC) by ribosome sometimes produces full-length proteins. We previously reported a readthrough of PTC of glycosyltransferase gene B4GALNT1 with hereditary spastic paraplegia (HSP). Here we featured the readthrough of B4GALNT1 of two mutants, M4 and M2 with PTC by immunoblotting and flow cytometry after transfection of B4GALNT1 cDNAs into cells. Immunoblotting showed a faint band of full-length mutant protein of M4 but not M2 at a similar position with that of wild-type B4GALNT1. AGC sequences at immediately before and after the PTC in M4 were critical for the readthrough. Treatment of cells transfected with mutant M4 cDNA with aminoglycosides resulted in increased readthrough of PTC. Furthermore, treatment of transfectants of mutant M2 cDNA with G418 also resulted in the induction of readthrough of PTC. Both M4 and M2 cDNA transfectants showed increased/induced bands in immunoblotting and GM2 expression in a dose-dependent manner of aminoglycosides. Results of mass spectrometry supported this effect. Here, we showed for the first time the induction and/or enhancement of the readthrough of PTCs of B4GALNT1 by aminoglycoside treatment, suggesting that aminoglycosides are efficient for patients with HSP caused by PTC of B4GALNT1, in which gradual neurological disorders emerged with aging.

scholarly journals Aminoglycoside-induced premature termination codon readthrough of COL4A5 nonsense mutations that cause Alport syndrome

2021 ◽  
Author(s):  
Kohei Omachi ◽  
Hirofumi Kai ◽  
Michel Roberge ◽  
Jeffrey H Miner
Keyword(s):  
Alport Syndrome ◽  
Premature Termination ◽  
Genetic Diseases ◽  
Premature Termination Codon ◽  
Full Length ◽  
Termination Codon ◽  
Reporter System ◽  
Nonsense Mutations ◽  
Type Iv ◽  
Genes Encoding

Alport syndrome (AS) is characterized by glomerular basement membrane (GBM) abnormalities leading to progressive glomerulosclerosis. Mutations in the COL4A3, COL4A4 or COL4A5 genes encoding type IV collagen α3α4α5 cause AS. Truncated α3, α4, and α5 chains lacking an intact COOH-terminal noncollagenous domain due to a premature termination codon (PTC) cannot assemble into heterotrimers or incorporate into the GBM. Therefore, achieving full-length protein expression is a potential therapy for AS caused by truncating nonsense mutations. Small molecule-based PTC readthrough (PTC-RT) therapy has been well studied in other genetic diseases, but whether PTC-RT is applicable to AS is unexplored. To investigate the feasibility of PTC-RT therapy in AS, we made a cDNA to express COL4A5 fused to a C-terminal NanoLuc luciferase (NLuc) to monitor full-length translation. Full-length COL4A5-NLuc produces luminescence, but mutants truncated due to a PTC do not. To screen for COL4A5 nonsense mutants susceptible to PTC-RT, we introduced 49 individual nonsense mutations found in AS patients into the COL4A5-NLuc cDNA. Luciferase assays revealed that 11 mutations (C29X, S36X, E130X, C1521X, R1563X, C1567X, W1594X, S1632X, R1683X, C1684X and K1689X) were susceptible to PTC-RT induced by G418, which is known to have high readthrough activity. Moreover, we found that some next-generation "designer" PTC-RT drugs induced RT, and RT enhancer compounds increased the efficacy of PTC-RT in a G418-susceptible PTC mutant. These results suggest that PTC-RT therapy is a feasible approach for some patients with AS. Our luciferase-based COL4A5 translation reporter system will contribute to further development of PTC-RT therapies in a personalized medicine approach to treating AS.

scholarly journals Aberrant splicing of the E-cadherin transcript is a novel mechanism of gene silencing in chronic lymphocytic leukemia cells

Blood ◽  
2009 ◽  
Vol 114 (19) ◽  
pp. 4179-4185 ◽  
Author(s):  
Sanjai Sharma ◽  
Alan Lichtenstein
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
Premature Termination ◽  
Ectopic Expression ◽  
Premature Termination Codon ◽  
Lymphocytic Leukemia ◽  
Termination Codon ◽  
Nonsense Mediated Decay ◽  
Aberrant Transcript ◽  
E Cadherin

Abstract Premature termination codon (PTC) mutations are due to insertion or deletion of nucleotides causing a frameshift and premature termination codon in RNA. These transcripts are degraded by the nonsense-mediated decay pathway and have a very short half-life. We used a microarray technique to screen for genes that up-regulate their RNA signal upon nonsense-mediated decay pathway blockade in chronic lymphocytic leukemia (CLL) specimens and identified an E-cadherin transcript with PTC. Sequencing revealed an aberrant E-cadherin transcript lacking exon 11, resulting in a frameshift and PTC. The aberrant E-cadherin transcript was also identified in normal B cells, but occurred at a much lower level compared with CLL cells. In CLL specimens, E-cadherin expression was depressed more than 50% in 62% cases (relative to normal B cells). By real-time polymerase chain reaction analysis, the relative amounts of wild-type transcript inversely correlated with amounts of aberrant transcript (P = .018). Ectopic expression of E-cadherin in CLL specimens containing high amounts of aberrant transcript resulted in down-regulation of the wnt–β-catenin pathway reporter, a pathway known to be up-regulated in CLL. Our data point to a novel mechanism of E-cadherin gene inactivation, with CLL cells displaying a higher proportion of aberrant nonfunctional transcripts and resulting up-regulation of the wnt–β-catenin pathway.

Sign in / Sign up

Export Citation Format

Share Document