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At least 163 records · Page 9Linked to original sources
PubMed2004

Studies on the regulation of the two-component histidine kinase gene CHK1 in Candida albicans using the heterologous lacZ reporter gene.

The two-component histidine kinase Chk1p of Candida albicans has been implicated in the regulation of cell wall biosynthesis. Deletion of CHK1 results in avirulence that in part may be due to the increased sensitivity of mutant strains to polymorphonuclear leukocytes. The mutant also does not adhere to human oesophageal tissue in vitro, probably as a consequence of its altered cell wall. In the current study, a CHK1 promoter-lacZ reporter (CHK1prlacZ) construct was expressed in wild-type C. albicans strain CAI4 and in two-component signal transduction mutants to determine the effect of environmental stress conditions on the regulation of CHK1 and the co-regulatory activities among these proteins. It is shown that lacZ expression varied according to the type of growth conditions and incubation time; expression was also influenced by the strain background. lacZ expression in CAI4 was greater at 37 degrees C and at a pH of 3.5 and in the presence of 4 mM H2O2, 0.1 mM menadione, 10 % serum or 1.5 M NaCl compared to cells grown at 30 or 42 degrees C. The increases in expression were time-dependent and not observed until cells were incubated for 120 min in these conditions (P < 0.05). As a correlate of the increase in transcription of CHK1-lacZ in the presence of H2O2, the chk1 mutant was more sensitive than wild-type and revertant cells to H2O2 in vitro. In addition to strain CAI4, we also measured CHK1p-lacZ reporter activity of mutants deleted in genes encoding other two-component proteins such as the response regulator gene SSK1, the histidine kinases, SLN1 and NIK1, and the HOG1 MAP kinase. Of these proteins, Ssk1p and Sln1p are presumed to mediate phosphotransfer to the HOG1 [hyperosmotic glycerol] MAP kinase pathway during oxidative and perhaps osmotic stress in C. albicans. Compared to strain CAI4, lacZ reporter activity increased significantly in the ssk1 mutant under all growth conditions after a 10 and 120 min incubation (P < 0.0001). lacZ expression in the ssk1 mutant was less at 42 degrees C compared to all other growth conditions (P < 0.05). Furthermore, lacZ reporter activity also increased in the hog1 mutant of C. albicans. These data suggest that SSK1 and HOG1 indirectly or directly negatively regulate CHK1 under most growth conditions tested. In the sln1 mutant, downregulation of CHK1 was observed in all growth conditions compared to strain CAI4 (P < 0.05), while regulation of lacZ in the nik1 mutant was similar to strain CAI4 except when cells were incubated in the presence of 4 mM H2O2 for 120 min (P < 0.05). Western blot analysis was used to determine the role of Chk1p in phosphorylation of Hog1p under oxidative or osmotic stress. It was found that Hog1p was phosphorylated in the chk1 mutant similar to wild-type CAF2-1 cells, although the temporal events of phosphorylation differed slightly in mutant cells. These results show that transcription of CHK1, as measured by the lacZ reporter assay, is statistically increased when cells are exposed to several types of stress or when incubated in 10 % serum in a mutant-specific background and at a specific time point. Of importance, our data also suggest that lacZ expression is indirectly or directly regulated by the HOG1 MAP kinase pathway, although a determination of its position in this pathway or in a cross-talking pathway awaits additional studies.

Blotting, Western↗
PubMed2005

Evolution of a length polymorphism in the human PER3 gene, a component of the circadian system.

Period homologue 3 (PER3) is a component of the mammalian circa-dian system, although its precise role is unknown. A biallelic variable number tandem repeat (VNTR) polymorphism exists in human PER3, consisting of 4 or 5 repeats of a 54-bp sequence in a region encoding a putative phosphorylation domain. This polymorphism has previously been reported to associate with diurnal preference ("morningness" and "eveningness") and delayed sleep-phase syndrome. We have investigated the global allele frequencies of this variant in ethnically distinct indigenous populations. All populations were polymorphic, with the shorter (4-repeat) allele ranging in frequency from 0.19 (Papua New Guinea) to 0.89 (Mongolia). To investigate if allele frequency has been influenced by natural selection, the authors 1) tested for a correlation with latitude and mean annual insolation (incident sunlight energy), using classical markers to correct for historical population differentiation; and they 2) compared allele-frequency difference between European American, African American, and East Asian populations, as measured using F(ST), to an empirical null distribution of F(ST)values based on a genome-wide dataset of single nucleotide polymorphisms (SNPs) of presumed neutral loci that were previously typed by The SNP Consortium. The variation in allele frequencies between indigenous populations did not show a pattern that would indicate selective pressure on PER3resulting from day-length variation or mean annual insolation, and the allele-frequency difference between European Americans, African Americans, and East Asians was not an outlier when compared to the distribution for presumed neutral SNPs. We therefore find no evidence for differential or balancing selection in the contemporary pattern of global PER3allele frequencies.

Circadian Rhythm↗
PubMedDate not supplied

Malazy, a degenerate, species-specific transposable element in Cercospora zeae-maydis.

Two fungal pathogens, Cercospora zeae-maydis Groups I and II, cause gray leaf spot of maize. During the sequencing of a cosmid library from C. zeae-maydis Group I, we discovered a sequence with high similarity to Maggy, a transposable element from Magnaporthe grisea. The element from C. zeae-maydis, named Malazy, contained 194-base-pair terminal repeats and sequences with high similarity to reverse transcriptase and integrase, components of the POL gene in the gypsy-like retrotransposons in fungi. Sequences with similarity to other POL gene components, protease and ribonuclease, were not detected in Malazy. A single copy of the element was detected by PCR and Southern analyses in all six North American isolates of C. zeae-maydis Group I but was not detected in the four isolates of C. zeae-maydis Group II from three continents or in phylogenetically related species. Fragments of the core domains of reverse transcriptase and integrase contained a high frequency of stop codons that were conserved in all six isolates of Group I. Additional C:G to T:A transitions in occasional isolates usually were silent mutations, while two resulted in isolate-specific stop codons. The absence of Malazy from related species suggests that it was acquired after the divergence of C. zeae-maydis Groups I and II. The high frequency of stop codons and the presence of a single copy of the element suggest that it was inactivated soon after it was acquired. Because the element is inactive and because reading frames for other genes were not found in sequences flanking the element, Malazy does not appear to be the cause of differences leading to speciation or genetic diversity between C. zeae-maydis Groups I and II.

Ascomycota↗
PubMed1994

Isolation and characterization of the gene encoding rat class theta glutathione S-transferase subunit yrs.

The rat gene encoding the class theta glutathione S-transferase (GST) subunit Yrs has been isolated from a rat lambda EMBL4 DNA library and completely sequenced. The gene spans approximately 4 kb comprising 5 exons separated by 4 introns, the smallest number of the gene components among known rat genes encoding GST subunits. Sequence analysis of the 5' flanking region of the GST Yrs gene indicated the absence of both TATA and CAAT boxes. However, potential binding sites for the transcription factors SP1, PU1, PEA3, and AP-2 were present in this region. Primer extension and 5'-rapid amplification of cDNA ends studies demonstrated the existence of multiple transcription initiation sites distributed over 58 bp in the upstream sequence from the translation initiation codon. The present study provides the first evidence for the primary structure of the gene encoding a class theta GST subunit.

Animals↗
PubMed1990

DNA polymorphism of the human complement component C7 gene in familial deficiencies.

A C7 cDNA probe detecting a TaqI restriction fragment length polymorphism has been used to examine the segregation of the "silent allele" (C7*Q0) in two familial deficiencies. Carrier diagnosis in healthy children is possible when both parents are heterozygotes. Only one of these two families was informative. The "silent allele" is linked to different TaqI alleles in both families. This suggests that at least two different C7*Q0 alleles are present in our population. This paper gives a protocol for genetic studies of hereditary traits in which the C7 gene and other genes tightly linked to it are involved.

Alleles↗
PubMed2006

Cloning and functional characterization of a fatty acid synthase component FAS2 gene from Saccharomyces kluyveri.

A gene coding the alpha subunit of fatty acid synthase (FAS2) was isolated from the budding yeast Saccharomyces kluyveri. Nucleotide sequence analysis indicated that this gene, termed Sk-FAS2, coded a protein having an amino acid sequence 83% identical to the FAS2 protein of S. cerevisiae (Sc-FAS2). The Sk-FAS2 gene was able to functionally complement an S. cerevisiae fas2 disruptant. This Sk-FAS2-expressing strain was found to produce larger amounts of C18 than C16, in contrast to the Sc-FAS2-expressing fas2 strain. In addition, fusion genes of Sk-FAS2 and Sc-FAS2 were transformed into a fas2-disrupted strain of S. cerevisiae, and fatty acid analysis of these transformants suggested that the region containing the acyl carrier protein and beta-ketoacyl reductase domains of yeast FAS2 protein play an important role in determining carbon chain length of fatty acids.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2003

Identification of recurrent mutations in the ARS (component B) gene encoding SLURP-1 in two families with mal de Meleda.

Mal de Meleda is a rare, autosomal recessive form of palmoplantar keratoderma. The disease has been mapped to chromosome 8qter, and in a recent study mutations in the ARS gene have been identified in families with this disorder. Here, we report two unrelated families with mal de Meleda, in which two different homozygous mutations in the ARS gene were identified. These findings support the notion that mutations in the ARS gene are pathogenic in mal de Meleda.

Adult↗
PubMed2000

Partial IFN-alpha/beta and IFN-gamma receptor knockout trisomy 16 mouse fetuses show improved growth and cultured neuron viability.

The trisomy 16 mouse fetus is a well-studied model for Down syndrome (trisomy 21), the leading genetic cause of mental retardation in the newborn population. Human chromosome 21 and mouse chromosome 16 each carry a large cluster of genes that code for components of the interferon (IFN)-alpha/beta and IFN-gamma receptors, and Down syndrome cells display significantly increased sensitivity to IFN action. We have previously reported that in utero anti-IFN IgG treatment of mice pregnant with trisomy 16 fetuses results in a significant improvement in trisomy 16 fetus growth and morphology and that anti-IFN-gamma IgG treatment can prevent the premature death of trisomy 16 fetal mouse cortical neurons in culture. We have now used IFN receptor subunit knockout mice to produce mouse fetuses that carry three No. 16 chromosomes and one copy each of disabled IFN-gamma receptor (IFNGR) and IFN-alpha/beta receptor (IFNAR-2) component genes. We report here that this partial IFN receptor knockout trisomy (PIRKOT) mouse fetus has significantly improved growth and yields cortical neurons whose viability is the equivalent of that seen in their euploid counterparts.

Animals↗
PubMed2005

Dietary components modify gene expression: implications for carcinogenesis.

Mouse genetic models that probe important pathways in intestinal cell maturation, such as cell-cycle regulation, apoptosis, and, especially, lineage specific differentiation, have provided profound insight into the underlying mechanisms of intestinal tumor formation and progression. However, a wealth of epidemiological and experimental data indicates that environment, especially the diet, is a principal determinant of relative risk for tumor development. We have demonstrated that even in mouse models in which tumor incidence is strongly initiated by genetic manipulation of genes, such as Apc, p21(WAF1/cip1), and p27(Kip1), a Western-style diet that is high in fat and low in calcium and vitamin D can dramatically increase and accelerate tumor formation. Moreover, experiments show that modulation of calcium and vitamin D levels can substantially influence tumor formation in both the mouse genetic models, as well as in a new dietary model that appears to mimic the development of sporadic colon cancer. Finally, analysis of gene expression profiles provides important insights into how diets may alter metabolic profiles and regulatory pathways that influence probability of tumor formation in the histologically and physiologically normal intestinal mucosa.

Animals↗