Conserved transcriptional regulation of a cone phototransduction gene in vertebrates.

cGMP-phosphodiesterase (PDE) is a key component in visual phototransduction. Rod and cone photoreceptors each produce their unique cGMP-PDE subunits. The alpha' catalytic subunits are believed to be cone-specific. In this study, we report that transfection of the -132 to +139 sequence in the upstream region of the human alpha'-PDE gene fused to luciferase cDNA gives the highest level of reporter gene transcription in cultured retinoblastoma Y79 cells. Transgenic Xenopus laevis carrying this sequence fused to green fluorescent protein (GFP) expressed GFP in cones, suggesting a conserved regulatory mechanism for alpha'-PDE transcription in both human and frog.

Transient transfection of human retinoblastoma cells : application to the analysis of the regulatory regions of photoreceptor-specific genes.

Retinoblastoma (Rb) is an intraocular tumor usually diagnosed in children under four years of age (1). The tumor rises when both alleles of the Rb tumor suppressor gene become inactivated in a retinal precursor cell during development (2,3). The first retinoblastoma cell line to be established in culture, Y-79 (4), has been shown to originate from neuroectodermal cells that express both neuronal and glial cell markers (3). Both Y-79 cells and Rb tumor cells produce mRNAs encoding several proteins unique to the photoreceptors (5), including different subunits of cone- and rod-specific cGMP-phosphodiesterases (6). Therefore, cultured Y-79 cells, which have a human retinal origin, could be particularly useful for studying the regulatory mechanisms of photoreceptor-specific gene expression (7).

UV-B induced differential transcription of psbD genes encoding the D2 protein of Photosystem II in the cyanobacterium Synechocystis 6803.

UV-B irradiation of intact Synechocystis sp. PCC 6803 cells results in the loss of Photosystem II activity, which can be repaired via de novo synthesis of the D1 and D2 reaction center subunits. A key step in the repair process is the differential transcription of the psbA2 and psbA3 genes, coding for identical D1 polypeptides [Máté et al. (1998) J Biol Chem 273: 17439-17444]. In the present work, we investigated for the first time the effect of UV-B irradiation on the transcription of the psbD1 and psbD2 genes encoding identical D2 polypeptides. By using gene-specific S1 nuclease protection assay we showed differential UV-B induced transcription of the two psbD genes: the level of psbD1 mRNA was increased 1.5-2 fold, whereas the accumulation of psbD2 mRNA was 5-7 fold. The induction of psbD2 transcript accumulation by low intensity light was specific for the UV-B range. UV-A emission from the applied UV source, as well as 100 muE m(-2) s(-1) white light had negligible effect. Increase in the psbD2 mRNA level was observed at very low UV-B intensities, which did not cause damage to the function and protein structure of PS II. Expression patterns of chimeric genes containing the promoter regions of the psbD1, psbD2 genes fused to the firefly luciferase (luc) reporter gene showed similar induction as observed for the endogenous psbD genes. Our findings demonstrate that UV-B radiation induces differential expression of the of the psbD1 and psbD2 genes. We propose that the primarily expressed psbD2 serves as a UV stress gene and participates in a rapid defense response against UV-B stress. This effect is regulated, at least partially, at the level of transcription.

[Malignant lymphoma associated with angioedema]. / Malignus lymphomákhoz társuló angiooedema.

The incidence of malignant lymphoma cases in constantly growing. Therefore it is worth-while to consider its presence even in cases where the symptoms do not give a clear indication of the disease. Two cases with angiooema being rare and not carachteristic signs for malignant lymphoma are reported. The authors discuss the supposed paraneoplastic patomechanism in malignant lymphoma, i.e. the possible role of C' 1 inhibition. In the view at the cases discussed the authors propose to consider the possible diagnosis of malignant lymphoma if unexplained angiooedema is present.

Isolation and characterization of a cDNA encoding the alpha' subunit of human cone cGMP-phosphodiesterase.

A human cDNA (alpha-PDE) encoding the alpha' catalytic subunit of cone photoreceptor cGMP-phosphodiesterase has been isolated and characterized. The nucleotide sequence of 2980 bp contains an open reading frame encoding an 859-amino-acid (aa) protein with a calculated molecular mass of 99 kDa. Northern blot analysis of human retinal mRNA hybridized with the alpha'-PDE cDNA revealed a signal corresponding to a 3.2-kb transcript. Comparison of the deduced aa sequence of human cone alpha'-PDE with corresponding proteins isolated from bovine and chicken retinas shows 89 and 83% identity, respectively, and indicates that alpha'-PDE has been very well conserved in the evolutionary process. Human cone alpha'-PDE is highly homologous to rod alpha-PDE and beta-PDE, suggesting that these proteins may have a close phylogenetic relationship.

Gene structure and amino acid sequence of the human cone photoreceptor cGMP-phosphodiesterase alpha' subunit (PDEA2) and its chromosomal localization to 10q24.

The genomic organization and nucleotide structure of the human cone photoreceptor cGMP phosphodiesterase alpha'-subunit (alpha'-PDE) gene (PDEA2) as well as its chromosomal localization have been determined. This gene, which spans about 48 kb, consists of 22 exons and codes for an 858-amino-acid protein. The alpha'-PDE gene maps to human chromosome 10q24. Its coding region shows about 90% nucleotide identity and 93% amino acid identity with the corresponding region of the bovine gene. The intron-exon organization of the genes encoding human cone alpha'-PDE and rod beta-PDE are very similar, suggesting that these proteins have a close phylogenetic relationship and probably a common origin.

Photoreceptor-specific mRNAs in mice carrying different allelic combinations at the rd and rds loci.

Several retinal mRNAs encoding photoreceptor-specific proteins have been examined in congenic lines of mice carrying different allelic combinations at the rd and rds loci, to determine how mRNA expression is affected by the presence of both the rd and rds genes together or by the presence of one or two rd and rds alleles in the visual cells. Slot blots with retinal RNA from 9 to 30 days old C3H +/+, +/+; rd/+, +/+; rd/rd, +/+; +/+, +/rds; +/+, rds/rds; and the rd/rd, rds/rds double homozygous mutant mice were hybridized successively to several [32P]cDNA probes encoding proteins involved in phototransduction. The increases and decreases in the levels of mRNA coding for opsin, the alpha-subunit of transducin, 48 kDa protein and the beta-subunit of cGMP-phosphodiesterase in the heterozygous and homozygous rds and rd mouse retinas reflected the growth and degeneration of the photoreceptor cells. The heterozygous rd mouse (rd/+, +/+) retina expressed cGMP-phosphodiesterase beta mRNA levels halfway between those in the control (+/+, +/+) and homozygous (rd/rd, +/+) mice, indicating a possible dosage effect. The double homozygous mutant (rd/rd, rds/rds) showed intermediate levels between those observed in the two homozygotes for all mRNAs studied, suggesting a possible interaction between the rd and rds genes.