scholarly journals Beta-thalassemia due to two novel nucleotide substitutions in consensus acceptor splice sequences of the beta-globin gene

Blood ◽  
1989 ◽  
Vol 73 (4) ◽  
pp. 914-918
Author(s):  
C Wong ◽  
SE Antonarakis ◽  
SC Goff ◽  
SH Orkin ◽  
BG Forget ◽  
...  
Keyword(s):  
Splice Site ◽  
Rna Splicing ◽  
Globin Gene ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Nucleotide Substitutions ◽  
Splice Site Selection ◽  
Exon 2 ◽  
Consensus Sequences ◽  
Beta Globin Gene

We have identified two novel RNA-splicing mutations affecting a critical nucleotide (nt) in the acceptor consensus sequences at both the IVS-1/exon 2 and IVS-2/exon 3 junctions of the human beta-globin gene. Both mutations are single nt substitutions, T to G and C to A, at position -3 adjacent to the invariant AG dinucleotide. For the IVS- 2/exon 3 mutation abnormal splicing into the cryptic splice site at IVS- 2 nt 579 is documented. Identification of these two mutations provides further support for the importance of the location of specific nucleotides within the consensus sequences in splice site selection and RNA processing.

scholarly journals Beta-thalassemia due to two novel nucleotide substitutions in consensus acceptor splice sequences of the beta-globin gene

Blood ◽  
1989 ◽  
Vol 73 (4) ◽  
pp. 914-918 ◽  
Author(s):  
C Wong ◽  
SE Antonarakis ◽  
SC Goff ◽  
SH Orkin ◽  
BG Forget ◽  
...  
Keyword(s):  
Splice Site ◽  
Rna Splicing ◽  
Globin Gene ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Nucleotide Substitutions ◽  
Splice Site Selection ◽  
Exon 2 ◽  
Consensus Sequences ◽  
Beta Globin Gene

Abstract We have identified two novel RNA-splicing mutations affecting a critical nucleotide (nt) in the acceptor consensus sequences at both the IVS-1/exon 2 and IVS-2/exon 3 junctions of the human beta-globin gene. Both mutations are single nt substitutions, T to G and C to A, at position -3 adjacent to the invariant AG dinucleotide. For the IVS- 2/exon 3 mutation abnormal splicing into the cryptic splice site at IVS- 2 nt 579 is documented. Identification of these two mutations provides further support for the importance of the location of specific nucleotides within the consensus sequences in splice site selection and RNA processing.

Nuclear pre-mRNA processing in plants: distinct modes of 3'-splice-site selection in plants and animals

1988 ◽  
Vol 8 (5) ◽  
pp. 2042-2051
Author(s):  
K Wiebauer ◽  
J J Herrero ◽  
W Filipowicz
Keyword(s):  
Splice Site ◽  
Hela Cells ◽  
Site Selection ◽  
Human Growth ◽  
Mrna Processing ◽  
Beta Globin ◽  
Splice Sites ◽  
Splice Site Selection ◽  
Consensus Sequences ◽  
Intron 2

The report that human growth hormone pre-mRNA is not processed in transgenic plant tissues (A. Barta, K. Sommergruber, D. Thompson, K. Hartmuth, M.A. Matzke, and A.J.M. Matzke, Plant Mol. Biol. 6:347-357, 1986) has suggested that differences in mRNA splicing processes exist between plants and animals. To gain more information about the specificity of plant pre-mRNA processing, we have compared the splicing of the soybean leghemoglobin pre-mRNA with that of the human beta-globin pre-mRNA in transfected plant (Orychophragmus violaceus and Nicotiana tabacum) protoplasts and mammalian (HeLa) cells. Of the three introns of leghemoglobin pre-mRNA, only intron 2 was correctly and efficiently processed in HeLa cells. The 5' splice sites of the remaining two introns were faithfully recognized, but correct processing of the 3' sites took place only rarely (intron 1) or not at all (intron 3); cryptic 3' splice sites were used instead. While the first intron in human beta-globin pre-mRNA was not spliced in transfected plant protoplasts, intron 2 processing occurred at a low level, indicating that some mammalian introns can be recognized by the plant intron-splicing machinery. However, excision of intron 2 proved to be incorrect, involving the authentic 5' splice site and a cryptic 3' splice site. Our results indicate that the mechanism of 3'-splice-site selection during intron excision differs between plants and animals. This conclusion is supported by analysis of the 3'-splice-site consensus sequences in animal and plant introns which revealed that polypyrimidine tracts, characteristic of animal introns, are not present in plant pre-mRNAs. It is proposed that an elevated AU content of plant introns is important for their processing.

scholarly journals The inactive beta globin gene on a gamma delta beta thalassemia chromosome has a normal structure and functions normally in vitro

Blood ◽  
1988 ◽  
Vol 71 (3) ◽  
pp. 766-770
Author(s):  
PT Curtin ◽  
YW Kan
Keyword(s):  
Globin Gene ◽  
Large Deletion ◽  
Beta Thalassemia ◽  
Ribonuclease Protection Assay ◽  
Beta Globin ◽  
Gamma Delta ◽  
Beta Globin Gene ◽  
Thalassemia Minor

We have previously described an English family with gamma delta beta- thalassemia in which a large deletion stops 25 kilobases (kb) upstream from the beta-globin gene locus, and yet the beta-globin gene is inactive in vivo. Affected family members had a beta-thalassemia minor phenotype with a normal hemoglobin A2 level. Gene mapping showed that these subjects were heterozygous for a chromosome bearing a large deletion that began in the G gamma-globin gene, extended through the epsilon-globin gene, and continued upstream for at least 75 kb. The A gamma-, delta-, and beta-globin gene loci on this chromosome were intact. To examine the possibility that an additional defect was present in the beta-globin gene, we cloned, sequenced, and examined the expression of the beta-globin gene from the affected chromosome. No mutation was found in the beta-globin gene sequence from 990 base-pairs 5′ to the cap site to 350 basepairs 3′ to the polyadenylation signal. The gene was subcloned into an expression vector and introduced into HeLa cells. Analysis of RNA derived from these cells, using a ribonuclease protection assay, revealed qualitatively and quantitatively normal transcription. Thus a structurally and functionally normal beta-globin gene is inactive in the presence of a large deletion more than 25 kb upstream. The loss of beta-globin gene function may be due to disturbance of chromatin conformation caused by the deletion or may be the result of loss of upstream sequences that are necessary for beta-globin gene expression in vivo.

scholarly journals Molecular analysis of Japanese delta beta-thalassemia

Blood ◽  
1988 ◽  
Vol 72 (5) ◽  
pp. 1771-1776
Author(s):  
S Shiokawa ◽  
H Yamada ◽  
Y Takihara ◽  
E Matsunaga ◽  
Y Ohba ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Beta Thalassemia ◽  
Globin Genes ◽  
Beta Globin ◽  
Beta Globin Gene ◽  
Gamma Globin ◽  
Large Deletions ◽  
Deletion Junction

A DNA fragment containing the deletion junction region from a Japanese individual with homozygous delta beta-thalassemia has been cloned. A clone containing the normal DNA surrounding the 3′ breakpoint of this deletion and a clone carrying the G gamma- and A gamma-globin genes of this patient were also isolated. Sequences of the deletion junction and both gamma-globin genes were determined. A comparison of these sequences with previously determined sequences of the normal counterparts revealed that the 5′ breakpoint is located between 2,134 and 2,137 base pairs (bp) 3′ to the polyA site of the A gamma-globin gene, the 5′ breakpoint is located just downstream of the 3′ border of the fetal gamma-globin duplication unit, and no molecular defects are evident within the gamma-globin gene region. A comparison between the sequences of the normal DNA surrounding the 3′ breakpoint and the normal DNA surrounding the 5′ breakpoint shows that deletion is the result of a nonhomologous recombination event. There are A+T-rich stretches near the 5′ and 3′ breakpoints in the normal DNA, and a portion of an Aly repeat is located in the region 3′ to the 3′ breakpoint. Southern blot analysis using probes 3′ to the beta-globin gene showed that the deletion extends in the 3′ direction further than any other deletions associated with delta beta-thalassemia and hereditary persistence of fetal hemoglobin (HPFH) heretofore reported. These results are discussed in terms of the mechanism generating large deletions in mammalian cells and three models for the regulation of gamma-globin and beta-globin gene expression in humans.

scholarly journals A novel mutation in the TATA box in a Japanese patient with beta +- thalassemia

Blood ◽  
1986 ◽  
Vol 67 (2) ◽  
pp. 547-550 ◽  
Author(s):  
Y Takihara ◽  
T Nakamura ◽  
H Yamada ◽  
Y Takagi ◽  
Y Fukumaki
Keyword(s):  
Novel Mutation ◽  
Globin Gene ◽  
Japanese Woman ◽  
Tata Box ◽  
Proximal Promoter ◽  
Base Substitution ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Beta Globin Gene

Abstract A single base substitution (A-G) at position -31 within the highly conserved proximal promoter element, the TATA box, was identified in the beta-globin gene cloned from a Japanese woman with beta +- thalassemia. It appears that she is homozygous for this specific allele, as determined by haplotype analysis using seven different polymorphic sites in the beta-globin gene cluster. Transient expression of the mutant gene in COS cells revealed a 45% reduction in beta-globin RNA production, relative to normal. These results establish the functional significance of the second base of the TATA box for in vivo transcription of the human beta-globin gene.

scholarly journals An approximately 300 bp deletion involving part of the 5' beta-globin gene region is observed in members of a Turkish family with beta- thalassemia

Blood ◽  
1987 ◽  
Vol 70 (2) ◽  
pp. 583-586 ◽  
Author(s):  
JC Diaz-Chico ◽  
KG Yang ◽  
A Kutlar ◽  
AL Reese ◽  
M Aksoy ◽  
...  
Keyword(s):  
Promoter Region ◽  
Genomic Dna ◽  
Restriction Site ◽  
Globin Gene ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Promoter Sequences ◽  
Beta Globin Gene ◽  
Turkish Family ◽  
Thalassemia Trait

Abstract Detailed gene mapping analyses of genomic DNA from two Turkish subjects with a beta-thalassemia trait demonstrated an approximately 300 bp deletion, which is located between the Rsa I restriction site 128 bp 5′ to the Cap site and the Acc I restriction site 284 bp 3′ to the same Cap site; it includes the 5′ beta promoter region, the first exon, and (part of) the IVS-I. Heterozygotes for this and two other beta- thalassemia types, which are also caused by deletions involving 5′ beta promoter sequences, appear to have higher hemoglobin (Hb) A2 levels, perhaps because the loss of this promoter results in an increased transcription of the delta globin gene, as delta and beta promoters may be influenced by the same enhancing sequences 3′ to the beta globin gene.

scholarly journals Observations on the levels of Hb A2 in patients with different beta- thalassemia mutations and a delta chain variant

Blood ◽  
1990 ◽  
Vol 76 (6) ◽  
pp. 1246-1249 ◽  
Author(s):  
JF Codrington ◽  
HW Li ◽  
F Kutlar ◽  
LH Gu ◽  
M Ramachandran ◽  
...  
Keyword(s):  
Promoter Activity ◽  
Globin Gene ◽  
Gene Promoter ◽  
General Mechanism ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Beta Chain ◽  
Beta Globin Gene ◽  
In Trans ◽  
In Cis

Abstract Hb A2 and its variant B2 (alpha 2 delta 2(16)(A13)Gly----Arg) were quantitated in the blood of subjects with three different types of beta- thalassemia and with the delta-B2 anomaly in cis or in trans to the beta-thalassemia determinant. In one family, the delta-B2 mutation was in cis to a newly discovered codon 47 (+A) frameshift. The levels of Hbs A2 and B2 were nearly the same and approximately 70% higher than those in simple Hb B2 heterozygotes. In two additional families, the delta-B2 variant was in trans to either a deletional beta-thalassemia (1,393 bp) involving part of the beta-globin gene and part of the beta- globin gene promoter, or to the -88 C----T promoter mutation. In both instances, the Hb B2 level was increased by approximately 80%, but the Hb A2 level was increased by approximately 270% and 200%, respectively. These data indicate two mechanisms that will cause an increase in delta chain production. One is consistent with a general mechanism concerning the relative excess of alpha chains in beta chain deficiencies which will combine with delta chains to form variable levels of Hb A2 dependent on the severity of the beta chain deficiency. The second concerns the loss of beta-globin gene promoter activity, perhaps by an absence of (or decreased) binding of specific protein(s) to this segment of DNA and a concomitant increase in delta-globin gene promoter activity in cis.

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