Association of hepatic nuclear factor-4 in the apolipoprotein B promoter: a preliminary report

Previous studies have examined the arrangement of regulatory elements along the apolipoprotein B (apoB) promoter region (-3067 to +940) and a promoter fragment extending from nucleotides -150 to +124 has been demonstrated to be essential for transcriptional activation of the apoB gene in hepatic and intestinal cells. It has also been shown that transcriptional activation of apoB requires a synergistic interaction between hepatic nuclear factor-4 (HNF-4) and CCAAT/enhancer-binding protein a (C/EBPa) transcription factors. Here, we have examined the hypothesis that HNF-4 factor binding to DNA may induce a DNA helix bend, thus facilitating the communication with a C/EBPa factor located one helix turn from this HNF-4 factor in the apoB promoter. A gel electrophoretic mobility shift assay using wild type double-stranded oligonucleotides or modified wild type duplex oligonucleotides with 10 nucleotides inserted between HNF-4 and C/EBPa factor motifs showed similar retarded complexes, indicating that HNF-4 and C/EBPa factors interact independently of the distance between binding sites. However, when only one base, a thymidine, was inserted at the -71 position of the apoB promoter, the complex shift was completely abolished. In conclusion, these results regarding the study of the mechanisms involving the interaction between HNF-4 and C/EBPa factors in the apoB promoter suggest that the perfect 5'-CCCTTTGGA-3' motif is needed in order to facilitate the interaction between the two factors.

Association of hepatic nuclear factor-4 in the apolipoprotein B promoter: a preliminary report.

Previous studies have examined the arrangement of regulatory elements along the apolipoprotein B (apoB) promoter region (-3067 to +940) and a promoter fragment extending from nucleotides -150 to +124 has been demonstrated to be essential for transcriptional activation of the apoB gene in hepatic and intestinal cells. It has also been shown that transcriptional activation of apoB requires a synergistic interaction between hepatic nuclear factor-4 (HNF-4) and CCAAT/enhancer-binding protein alpha (C/EBP alpha) transcription factors. Here, we have examined the hypothesis that HNF-4 factor binding to DNA may induce a DNA helix bend, thus facilitating the communication with a C/EBP alpha factor located one helix turn from this HNF-4 factor in the apoB promoter. A gel electrophoretic mobility shift assay using wild type double-stranded oligonucleotides or modified wild type duplex oligonucleotides with 10 nucleotides inserted between HNF-4 and C/EBP alpha factor motifs showed similar retarded complexes, indicating that HNF-4 and C/EBP alpha factors interact independently of the distance between binding sites. However, when only one base, a thymidine, was inserted at the -71 position of the apoB promoter, the complex shift was completely abolished. In conclusion, these results regarding the study of the mechanisms involving the interaction between HNF-4 and C/EBP alpha factors in the apoB promoter suggest that the perfect 5'-CCCTTTGGA-3' motif is needed in order to facilitate the interaction between the two factors.

[Cryptococcus neoformans chemotyping. Review of the literature. New epidemiologic data on cryptococcosis. Our experience with the use of C.G.B. media in the study of this yeast]. / Quimiotipagem do Cryptococcus neoformans. Revisão da literatura. Novos dados epidemiológicos sobre a criptococose. Nossa experiência com o emprego do meio de C.G.B. no estudo daquela levedura.

The purpose of this work was to collect the main information from the literature about the biotyping of Cryptococcus neoformans. The more up-to date research concerning the epidemiology of cryptococcosis comprising quite a few articles, mainly after the advent of AIDS, was also reviewed. The Cryptococcus neoformans varieties neoformans and gattii are well defined biochemically nowadays chiefly through the C.G.B. medium, according to Kwon-Chung et al. (1982). The isolation of C. neoformans var. gattii from flowers and leaves of Eucalyptus camaldulensis and Eucalyptus tereticornis, specially in Australia, through the works of Ellis & Pfeiffer (1990) and Pfeiffer & Ellis (1992) permitted very interesting epidemiological investigations on C. neoformans, a capsulated yeast by which Sanfelice, in Italy (1894; 1895) attracted attention of medical class. Busse, in 1894, described the first human case of cryptococcosis under the presentation of a bone lesion simulating sarcoma. In this paper, the Brazilian researchers focused on this subject were pointed out, followed by the Author's experience with the C.G.B. medium (L-canavanine, glycine and bromothymol blue) proposed by Kwon-Chung et al. (1982) with very good results. It was possible with such medium the study of 50 C.N.S. liquor samples, being 39 from AIDS patients (78%) and 11 from non-AIDS ones (22%). Thirty-seven out of the 39 HIV-positive patients (74%) were identified as C. neoformans var. gattii. From the negative HIV, 8 (16%) were classified as C. neoformans var. neoformans and 3 (6%) as C. neoformans var. gattii. We could not perform the serotyping of the above referred samples. It is evident anyway that in Brazil there exist both varieties gattii and neoformans, agents of neurocryptococcosis, including AIDS patients. The importance of neurocryptococcosis, mainly among AIDS patients, is stressed here, showing once more the value of C.G.B. medium in the typing of C. neoformans in its two varieties. Also, it is of relevant importance the demonstration that some species of eucalyptus may act as "host-trees" of C. neoformans var. gattii.