The molecular basis for the genetic polymorphism of thiopurine S -
methyltransferase (TPMT) has been estab-lished for Caucasians, but it
remains to be elucidated in African populations. In the current study, we
determined TPMT genotypes in a population of 248 African-Americans and
compared it with allele frequencies in 282 Caucasian Americans. TPMT
genotype was determined in all individuals with TPMT activity indicative of
a heterozygous genotype (</=10.1 U/ml pRBC, n = 23African- Americans, n
= 21 Caucasians) and a control group with TPMT activity indicative of a
homozygous wild-type genotype (>10.2 U/ml pRBC, n = 23
African-Americans, n = 21 Caucasians). No mutant alleles were found in the
high activity control groups. The overall mutant allele frequencies were
similar in African-Americans and Caucasians (4.6 and 3.7% of alleles,
respectively). However, while TPMT*3C was the most prevalent mutant allele
in African-Americans (52.2% of mutant alleles), it represented only 4.8% of
mutant alleles in Caucasians ( P < 0.001). In contrast, TPMT*3A and
TPMT*2 were less common in African-Americans (17.4 and 8.7% of mutant
alleles), whereas TPMT*3A was the most prevalent mutant allele in
Caucasians (85.7% of mutant alleles). A novel allele ( TPMT*8 ), containing
a single nucleotide transition (G644A), leading to an amino acid change at
codon 215 (Arg-->His), was found in one African-American with
intermediate activity. These data indicate that the same TPMT mutant
alleles are found in American black and white populations, but that the
predominant mutant alleles differ in these two ethnic groups.
相似文献
Specific interactions between the 72-amino acid nucleocapsid protein NCp7 of the human immunodeficiency virus, type 1 and the genomic RNA are essential for virus replication. Studies on the mechanism of action of NCp7 require a direct visualization of its complexes with nucleic acids and the determination of binding affinities. To facilitate these investigations, fluorescent NCp7 derivatives were developed by introduction in the NCp7 sequence of a non-natural amino acid, (S)-β-(9-acridinyl)alanine (Aca) obtained by a chiral synthetic method. Three fluorescent NCp7 derivatives were obtained by introducing this amino acid at different positions. As shown by NMR, the three-dimensional structure of NCp7 is not altered by introduction of Aca. The fluorescent peptides were found to be as potent as their precursors in interacting with nucleic acids and in promoting HIV-1 genomic RNA dimerization. Moreover, because of their fluorescent properties, these NCp7s can be used at submicromolar concentrations to directly visualize and quantify protein-nucleic acid interactions in solution or after gel electrophoresis. This could facilitate the development of new antiviral agents aimed at inhibiting the functions of NCp7 and studies on the intracellular traffic of NCp7 within the preintegration complex. 相似文献
Sirtuin 3 is a nicotinamide adenine dinucleotide dependent mitochondrial deacetylase that governs mitochondrial metabolism and oxidative defense. The demise in myocardial function following myocardial ischemia has been associated with mitochondrial dysfunction. Sirt3 maintains myocardial contractile function and protects from cardiac hypertrophy. The role of Sirt3 in ischemia is controversial. Our objective was to understand, under what circumstances Sirt3 is protective in different facets of ischemia, using an in vitro proof-of-concept approach based on simulated ischemia in cultured cardiomyoblasts. Cultured H9c2 cardiomyoblasts were subjected to hypoxia and/or serum deprivation, the combination of which we refer to as simulated ischemia. Apoptosis, as assessed by Annexin V staining in life-cell imaging and propidium-iodide inclusion in flow cytometry, was enhanced following simulated ischemia. Interestingly, serum deprivation was a stronger trigger of apoptosis than hypoxia. Knockdown of Sirt3 further increased apoptosis upon serum deprivation, whereas no such effect occurred upon additional hypoxia. Similarly, only upon serum deprivation but not upon simulated ischemia, silencing of Sirt3 led to a deterioration of mitochondrial function in extracellular flux analysis. In the absence of oxygen these Sirt3-dependent effects were abolished. These data indicate, that Sirt3-mediated myocardial protection is oxygen-dependent. Thus, mitochondrial respiration takes center-stage in Sirt3-dependent prevention of stress-induced myocardial damage.
