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Biomedical subjects

A Economou

Publications and source records attributed to A Economou.

65 records · Page 4Linked to original sources

Structure and function of the Epstein-Barr virus BZLF1 protein.

Five DNA-binding sites for the Epstein-Barr virus BZLF1 protein have been identified within three of the early viral promoters, and four of these binding sites contain a consensus AP-1 site. The part of the BZLF1 protein required for sequence-specific DNA binding to one of these AP-1-like sites was identified by deletion mapping. Site-directed mutagenesis of this DNA target suggests that BZLF1 may work partly by overcoming a cellular repressor of viral transcription.

Amino Acid Sequence↗

The terminal protein gene 2 of Epstein-Barr virus is transcribed from a bidirectional latent promoter region.

The intact terminal protein genes (TP1 and TP2) of Epstein-Barr virus (EBV) are created upon infection by circularization of the linear viral genome at its terminal repeats. The structure of the 1.7 kb TP2 latent mRNA has been determined by cDNA analysis and Northern blotting, revealing its close relation to TP1 mRNA. The 1.7 kb transcript is expressed from a different promoter and has a different 5' exon from TP1 but is also spliced across the terminal repeats. The last eight exons are common to the TP1 and TP2 RNAs. The TP2 promoter is 3.3 kb downstream of the TP1 promoter and is part of a bidirectional latent EBV promoter region transcribing the TP2 and the latent membrane protein RNAs in opposite directions.

Cloning, Molecular↗

Transcription of rhiA, a gene on a Rhizobium leguminosarum bv. viciae Sym plasmid, requires rhiR and is repressed by flavanoids that induce nod genes.

Strains of Rhizobium leguminosarum biovar viciae specifically make an abundant protein (Rhi) in free-living culture but not in bacteroids. Genes needed for Rhi synthesis are on a Sym plasmid and here we show that one of these genes, rhiA, is the structural gene that specifies this polypeptide. Transcription of rhiA requires a regulatory gene, rhiR, located close to rhiA and to nod genes involved in nodulation. Mutations in rhiA or rhiR do not appear to affect symbiotic nitrogen fixation. Transcription of rhiA is repressed in cells grown in the presence of the flavanone hesperetin or the flavone apigenin, both of which are potent inducers of transcription of nod genes. This was deduced from the use of rhiA-lacZ fusions; however, when the Rhi polypeptide was detected in SDS gels, there was no apparent difference in the intensity of its staining in extracts obtained from cells grown with or without these flavanoid nod gene inducer molecules. However, a mutation in a nodulation gene, nolR, also closely linked to the nod and rhi genes, caused a severe depression in the amount of Rhi (as seen on gels) that was made in cells grown in the presence of inducer flavanoids.

Bacterial Proteins↗

Fine needle aspiration biopsy cytology in the diagnosis of thyroid cancer: comparative study of 213 operated patients.

Between 1982 and 1984, fine needle aspiration biopsy cytology (ABC) was performed in 1100 patients (aged 14-80, 993 women), with nodular goitre, who had either a solitary cold nodule or dominant hypofunctioning nodule(s) within a multinodular or diffusely enlarged gland. Surgery was performed in 213 patients based on clinical and cytological criteria, and the histology of the surgical specimens was correlated with the cytological findings. ABC specimens were sufficient for cytological diagnosis in 190 patients and were classified as malignant (positive), suspicious or benign. In 37 patients who had a final histological diagnosis of malignancy, cytology was positive or suspicious in 33 and benign in 4. In the remaining 153 patients with benign histology there were 7 positive or suspicious aspirates, and 146 benign. The 37 malignancies included papillary carcinomas in 26 patients (24 positive or suspicious and 2 benign on cytology), Hürthle-cell tumours in 6 (6 positive), follicular carcinoma in 1 (negative), anaplastic carcinoma in 1 (suspicious), medullary carcinoma in 2 (1 positive, 1 negative), and lymphoma in 1 (positive). Our results indicate that the overall sensitivity rate of the ABC method for cancer was 89.2 per cent, the diagnostic specificity 95.4 per cent, the false-positive rate 17.5 per cent and the false negative rate 2.6 per cent. The overall accuracy of the method was 94.2 per cent. It is concluded that papillary and Hürthle-cell carcinomas can be diagnosed accurately with ABC but we recommend that the method be used in conjunction with clinical information and other conventional diagnostic procedures.

Adolescent↗