Identification of Alternative First Exons of NADH-Cytochrome b5Reductase Gene Expressed Ubiquitously in Human Cells

Du, Minjie; Shirabe, Komei; Takeshita, M

doi:10.1006/bbrc.1997.6873

Cited by 11 publications

(9 citation statements)

References 19 publications

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“…The ubiquitous expression of the 1S\1SSh-type transcript is consistent with the analysis of the 5h flanking region of exon 1S devoid of consensus sequences for erythroid transcription factors NF-E2 and GATA-1 [27]. In addition to one GT box (GGTGGGTGG) already mentioned and two overlapping GC boxes (CCGCCC) [25], we observed the presence of a putative binding site for nuclear factor κB (GGGGATTACC) ( Figure 1) and, 190 nt upstream of exon 1S, a complete 258 bp Alu repeated sequence in the opposite orientation to that of the b & R gene. This Alu element shows 86 % identity with the consensus sequence of the class II Alu subfamily, the most represented class (more than 400 000 copies per genome), thought to have been inserted into the primate genome 32-57 million years ago [29][30][31].…”

Section: Discussionsupporting

confidence: 87%

Transcriptional and translational mechanisms of cytochrome b5 reductase isoenzyme generation in humans

2001

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Cytochrome b5 reductase (b5R) is an essential enzyme that exists in soluble and membrane-bound isoforms, each with specific functions. In the rat, the two forms are generated from alternative transcripts differing in the first exons. In contrast, the biogenesis of b5R isoforms in the human is not yet well understood. In the present study we have detected three novel alternative exons, designated 1S, S' and 1B, located between the first alternative exon 1M and the common second exon in the human b5R gene. Accordingly, multiple M-type, S-type and SS'-type and B-type transcripts are generated. All types of human b5R transcript are expressed ubiquitously. An analysis of in vitro translation products demonstrated an alternative use of different AUG initiators resulting in the production of various human b5R protein isoforms. Our results indicate that the organization of the 5' region of the b5R gene is not conserved between rodents and humans. Insertion of Alu elements into the human b5R gene, in particular just upstream of the S/S' region, could be responsible for dynamic events of gene rearrangement during evolution.

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Section: Discussionsupporting

confidence: 87%

Transcriptional and translational mechanisms of cytochrome b5 reductase isoenzyme generation in humans

2001

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“…Each gene generates two major splice variants, a soluble cytosolic form found in erythrocytes, and a membrane-bound protein predominantly located in the endoplasmic reticulum of hepatocytes and other tissues [11–13]. However, individual variability in the expression of CYB5R3 and CYB5A has not been well characterized.…”

Section: Introductionmentioning

confidence: 99%

Cytochrome b5 and NADH cytochrome b5 reductase: genotype–phenotype correlations for hydroxylamine reduction

Sacco¹,

Trepanier²

2010

Pharmacogenetics and Genomics

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Objectives-NADH cytochrome b 5 reductase (b5R) and cytochrome b 5 (b5) catalyze the reduction of sulfamethoxazole hydroxylamine (SMX-HA), which can contribute to sulfonamide hypersensitivity, to the parent drug sulfamethoxazole. Variability in hydroxylamine reduction could thus play a role in adverse drug reactions. The aim of this study was to characterize variability in SMX-HA reduction in 111 human livers, and investigate its association with single nucleotide polymorphisms (SNPs) in b5 and b5R cDNA.Methods-Liver microsomes were assayed for SMX-HA reduction activity, and b5 and b5R expression was semi-quantified by immunoblotting. The coding regions of the b5 (CYB5A) and b5R (CYB5R3) genes were resequenced.Results-Hepatic SMX-HA reduction displayed a 19-fold range of individual variability (0.06-1.11 nmol/min/mg protein), and a 17-fold range in efficiency (V max /K m ) among outliers. SMX-HA reduction was positively correlated with b5 and b5R protein content (p < 0.0001, r = 0.42; p = 0.01, r = 0.23, respectively), and expression of both proteins correlated with one another (p < 0.0001; r = 0.74). A novel cSNP in CYB5A (S5A) was associated with very low activity and protein expression. Two novel CYB5R3 SNPs, R59H and R297H, displayed atypical SMX-HA reduction kinetics and decreased SMX-HA reduction efficiency.Conclusion-These studies indicate that while novel cSNPs in CYB5A and CYB5R3 are associated with significantly altered protein expression and/or hydroxylamine reduction activities, these low frequency cSNPs only appear to minimally impact overall observed phenotypic variability. Work is underway to characterize polymorphisms in other regions of these genes to further account for individual variability in hydroxylamine reduction.

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“…In addition to one GT box (GGTGGGTGG) already mentioned and two overlapping GC boxes (CCGCCC) [25], we observed the presence of a putative binding site for nuclear factor κB (GGGGATTACC) (Figure 1) and, 190 nt upstream of exon 1S, a complete 258 bp Alu repeated sequence in the opposite orientation to that of the b & R gene. This Alu element shows 86 % identity with the consensus sequence of the class II Alu subfamily, the most represented class (more than 400 000 copies per genome), thought to have been inserted into the primate genome 32-57 million years ago [29][30][31].…”

Section: Discussionmentioning

confidence: 53%

“…Sequencing of remaining cDNA clones revealed three types of novel sequence located 5h to the second common exon. In all investigated tissue, the majority of the 5h-end b & R cDNA clones contained the 1S exon partly described by Du et al [25], for which the 3h border corresponds to position nt 2852 in the human gene [21]. However, most of the 1S-type transcripts were extended by a 5h 161 bp novel fragment, bounded by TGGGATCC repeats (Figure 1).…”

Section: Characterization By 5h Race Pcr Of Various B 5 R Transcriptsmentioning

confidence: 74%

Transcriptional and translational mechanisms of cytochrome b5 reductase isoenzyme generation in humans

Leroux

Mota-Vieira

Kahn

2001

Biochemical Journal

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Cytochrome b5 reductase (b5R) is an essential enzyme that exists in soluble and membrane-bound isoforms, each with specific functions. In the rat, the two forms are generated from alternative transcripts differing in the first exons. In contrast, the biogenesis of b5R isoforms in the human is not yet well understood. In the present study we have detected three novel alternative exons, designated 1S, S′ and 1B, located between the first alternative exon 1M and the common second exon in the human b5R gene. Accordingly, multiple M-type, S-type and SS′-type and B-type transcripts are generated. All types of human b5R transcript are expressed ubiquitously. An analysis of in vitro translation products demonstrated an alternative use of different AUG initiators resulting in the production of various human b5R protein isoforms. Our results indicate that the organization of the 5′ region of the b5R gene is not conserved between rodents and humans. Insertion of Alu elements into the human b5R gene, in particular just upstream of the S/S′ region, could be responsible for dynamic events of gene rearrangement during evolution.

show abstract

Identification of Alternative First Exons of NADH-Cytochrome b5Reductase Gene Expressed Ubiquitously in Human Cells

Cited by 11 publications

References 19 publications

Transcriptional and translational mechanisms of cytochrome b5 reductase isoenzyme generation in humans

Transcriptional and translational mechanisms of cytochrome b5 reductase isoenzyme generation in humans

Cytochrome b5 and NADH cytochrome b5 reductase: genotype–phenotype correlations for hydroxylamine reduction

Transcriptional and translational mechanisms of cytochrome b5 reductase isoenzyme generation in humans

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