Two novel arrangements of the human fetal globin genes: G gamma-G gamma and A gamma-A gamma.

We describe two novel arrangements of the human fetal globin gene region: one chromosome with two linked A gamma genes (A gamma-A gamma) and two chromosomes with two linked G gamma genes (G gamma-G gamma). The gamma genes of these three chromosomes were cloned and the unusual 5' A gamma gene and one of the unusual 3' G gamma genes were partially sequenced. Both of these unusual genes differ from the genes normally found at their respective locations by a nucleotide substitution at the site of the single coding region difference between normal G gamma and A gamma genes. In both cases, the substitution is identical to the nucleotide found at that position in the normal neighboring gene. The unusual 3' G gamma gene also differs from normal A gamma genes at two other nucleotide positions, but both differences appear to be "private" or exclusive to this particular gene. These unusual fetal globin gene arrangements could have arisen from point mutations or from gene conversions of limited extent, the boundaries of which have been determined for all three chromosomes.     

Differential syncytium-inducing capacity of human immunodeficiency virus isolates: frequent detection of syncytium-inducing isolates in patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex.

Human immunodeficiency virus isolates were studied with respect to syncytium-inducing capacity, replicative properties, and host range. Five of 10 isolates from patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex were able to induce syncytia in cultures of peripheral blood mononuclear cells (MNC). In contrast, only 2 of 12 isolates from asymptomatic individuals had syncytium-inducing capacity. Syncytium-inducing isolates were reproducibly obtained from the same MNC sample in over 90% of the cases, independent of the donor MNC used for propagation. Syncytium-inducing capacity was shown to be a stable property of an isolate, independent of viral replication rates. Evidence was obtained that the high replication rate of syncytium-inducing isolates observed during primary isolation may be due to higher infectivity of these isolates. The finding that only syncytium-inducing isolates could be transmitted to the H9 cell line is compatible with this higher infectivity. The frequent isolation of syncytium-inducing isolates from individuals with AIDS-related complex or AIDS and the apparent higher in vitro infectivity of these isolates suggest that syncytium-inducing isolates may unfavorably influence the course of human immunodeficiency virus infection.     

壮族新生儿胎儿血红蛋白中G_γ与A_γ比值测定及其异常者基因图谱分析

本文叙述聚丙烯酰胺凝胶电泳法测定449例广西壮族新生儿脐带血中Gγ/Aγ比值,其中部分采用HPLC方法进行比较分析。结果显示低Gγ值(20—48％)和高Gγ值(81—85％)比例相同,占2.45％。对其中两例低Gγ值和两例高Gγ值者的杂色体DNA进行基因图谱分析,确定其基因型分别为-GAγ-/-Gγ-Aγ-,-Gγ-AGγ-Aγ-/-Gγ-Aγ-。     

Role of the sfiA-dependent cell division regulation system in Escherichia coli.

Several authors have suggested that the SOS-associated (sfiA-dependent) system of division inhibition, normally induced by perturbations of DNA replication, also regulates steady-state (unperturbed) cell division. The present work shows that mean cell mass is identical in sfiA+ and sfiA mutant cultures during steady-state growth, that mass adjustment is identical after shift up, that sfiA expression is not induced by shift up, and that a sfiA mutation does not cause aberrant chromosome segregation.     

Quantitative evaluation of recA gene expression in Escherichia coli

Summary A recA::lac operon fusion was constructed using the phage Mu d(Ap, lac) in Escherichia coli to obtain precise measurements of the level of recA gene expression in various genetic backgrounds. The RecA protein normally represents 0.02% of total protein. This value is known to increase dramatically after treatments interrupting DNA synthesis; kinetic experiments showed that the rate of recA expression increases 17-fold within 10 min after UV irradiation or thymine starvation. In mutants affected in SOS regulation or repair the following observations were made: (i) the tif-1 mutation in the recA gene does not alter the basal level of recA expression, suggesting that it improves the protease activity of RecA; (ii) the lexA3 mutation does not create a super-repressor of recA; (iii) the tsl-1 mutation in the lexA gene makes the LexA protein a poor repressor of recA at 30°C (2.5-fold derepression) and a poor substrate for RecA protease (3-fold stimulation of recA expression by UV); (iv) the spr-55 amber mutation in the lexA gene causes a 30-fold increase in recA expression, higher than all inducing treatments, and this level cannot be further increased by nalidixic acid; (v) the zab-53 mutation at the recA locus, known to abolish tsl-mediated induction of recA expression, is trans-recessive and thus probably affects a regulatory site on the DNA; (vi) uvrA, B and C, recB and recF mutations do not increase the basal level of recA expression, suggesting that there are not sufficient spontaneous lesions to cause induction even when any one of these three repair pathways is inoperative.Abbreviations Ap ampicillin - Km kanamycin - Cm chloramphenicol - Tc terracycline - Sm streptomycin - Ts thermosensitive - Tr thermoresistant - Nal nalidixic acid - X-Gal 5-bromo-4-chloro-3-indolyl--D-galactoside - mito C mitomycin C - LFT low frequency transducing - HFT high frequency transducing     

Neutralization of feline immunodeficiency virus by polyclonal feline antibody: simultaneous involvement of hypervariable regions 4 and 5 of the surface glycoprotein.

Sites involved in antibody-mediated neutralization of feline immunodeficiency virus were mapped by reciprocal exchange of envelope fragments or amino acids between molecular clones of feline immunodeficiency virus with different susceptibilities to neutralization by a polyclonal cat serum. Combinations of mutations within HV-4 or within HV-4 and HV-5 changed the susceptibility of the viruses to neutralizing antibody.     

Sickle cell anemia,sickle cell β-thalassemia,and thalassemia major in Albania: characterization of mutations

We have analyzed the hemoglobin abnormalities in nearly 50 Albanian patients with a significant hemoglobinopathy and included 37 relatives in this study. Sickle cell anemia (SS) is a common disorder; all 15 sickle cell anemia patients had the complications expected for this disease. The ^s haplotype was type 19 (Benin); -thalassemia-2 was rare. Three -thalassemia alleles (IVS-I-110, GA; codon 39, CT; IVS-I-6, TC) were present in nearly 85% of the -thalassemia alleles; their frequencies were intermediate between those observed in the populations of neighboring countries. A few rare mutations were also found, which might have originated in India, Turkey, Macedonia, and Greece. Nearly all patients with Hb S--thalassemia had the IVS-I-110 (GA) mutation. The frequencies of 11 -thalassemia mutations in 17 mostly Mediterranean countries have been reviewed.     

Hb Costa Rica or · 2 ‚ 277(EF1)His→Arg: the first example of a somatic cell mutation in a globin gene

We have identified a minor hemoglobin component (∼5%) in the blood of a healthy Costa Rican female, but not in her mother and two brothers (father not studied), that has an His→Arg replacement at position β77 (Hb Costa Rica). No other amino acid replacements were observed and no β- or γ-chain-like peptides were present. Hb Costa Rica has a normal stability. Sequence analyses of numerous polymerase chain reaction (PCR)-amplified segments of DNA that contain exon 2 of the β gene failed to identify a CAC→CGC (His→Arg) mutation. The same was the case when cDNA was sequenced, indicating that a β-Costa Rica-mRNA could not be detected with this procedure. Gene mapping of genomic DNA with BglII, BamHI, and HindIII gave normal fragments only and with the same intensity as observed for the fragments of a normal control. The quantities of the β chain variants Hb J-Iran and Hb Fukuyama with related mutations at β77 vary between 30% and 45% in heterozygotes, whereas that of Hb F-Kennestone with the same His→Arg mutation but in the ^Gγ-globin gene, is a high 40%–45% (as percentage of total ^Gγ) in a heterozygous newborn. These different observations exclude a heterozygosity of the A→G mutation at codon β77, as well as a deletion comparable to that of Hbs Lepore or Kenya, or a β-globin gene duplication, and point to a nontraditional inheritance of Hb Costa Rica. Allele-specific amplification of cDNA with appropriate primers identified the presence of a low level of mutated mRNA in the reticulocytes of the patient, which was confirmed by dotblot analysis of the same material with ³²P-labeled probes. Comparable amplification products were not observed in genomic DNA. The A→G mutation apparently occurred in a somatic cell at a relatively early stage in the development of the hematopoietic cell system, and Hb Costa Rica accumulated through rapid cell divisions in patchy areas in the bone marrow (somatic mosaicism). An unequal distribution of Hb Costa Rica over the red cells supports this possibility. Received: 25 August 1995 / Revised: 13 December 1995