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P Alano

Publications and source records attributed to P Alano.

30 records · Page 2Linked to original sources
PubMed1992

Gene inactivation of Pf11-1 of Plasmodium falciparum by chromosome breakage and healing: identification of a gametocyte-specific protein with a potential role in gametogenesis.

We report the identification of the product of the Plasmodium falciparum Pf11-1 gene and demonstrate that it is a gametocyte-specific protein that has a potential role in the rupture of the host erythrocyte and emergence of the gametes (gametogenesis). The Pf11-1 gene is a large locus (30 kb) whose sequence predicts a glutamic acid-rich polypeptide. Our identification of the Pf11-1 gene product as gametocyte specific was greatly facilitated by the isolation of a mutant parasite clone in which greater than 90% of the Pf11-1 gene was deleted. Molecular analysis of the mutant locus suggests that the underlying genetic mechanism is chromosome breakage and subsequent healing by the addition of telomere repeats. PCR-based analysis showed that similar DNA rearrangements occur commonly in small subpopulations of most laboratory strains, suggesting that the Pf11-1 locus represents a fragile chromosome region. Northern blot analysis demonstrates that a large Pf11-1 gene-specific transcript (much greater than 10 kb) is present in gametocytes but not in asexual blood stage parasites. The Pf11-1 protein was localized by electron microscopy to granules in the cytoplasm of gametocytes adjacent to the membrane of the parasitophorous vacuole. Following in vitro stimulation of gametogenesis, the Pf11-1 protein was found in the membrane of lysed erythrocytes, suggesting a role for Pf11-1 in erythrocyte rupture within the mosquito gut.

Animals↗
PubMed1992

Characterization of a Plasmodium falciparium mutant that has deleted the majority of the gametocyte-specific Pf11-1 locus.

We identified a gametocyte-specific protein of Plasmodium falciparum called Pf11-1 and provide experimental evidence that this molecule is involved in the emergence of gametes of the infected erythrocyte (gametogenesis). A mutant parasite clone, which has deleted over 90% of the Pf11-1 gene locus, was an important control to establish the gametocyte-specific expression of the Pf11-1. Molecular analysis of the Pf11-1 deletion indicates that it is presumably due to a chromosome breakage with subsequent 'healing' by the addition of telomeric heptanucleotides. Moreover, similar DNA rearrangements are observed in most of the laboratory isolates during asexual propagation in vitro.

Animals↗
PubMed1991

DNA polymerase delta: gene sequences from Plasmodium falciparum indicate that this enzyme is more highly conserved than DNA polymerase alpha.

Genes encoding proteins homologous to the catalytic subunits of DNA polymerase alpha and delta have been cloned from the human malaria parasite Plasmodium falciparum. These are among the first cellular replicative DNA polymerase genes to be cloned and their sequences allow us to make new statements about the relative degrees of conservation of these two enzymes. The most important finding was that P. falciparum Pol delta showed considerable homology to the only other Pol delta enzyme for which published sequence is available, that of S. cerevisiae, displaying an overall amino acid identity of 45% and identity over a highly conserved central region of 59%. In contrast, the level of identity shown over the equivalent central region of Pol alpha between the P. falciparum and S. cerevisiae sequences is only 32%. The sequence data also allowed us to examine the degree of conservation in putative exonuclease domains of Pol delta. The Pol delta gene of P. falciparum maps to chromosome 10 and evidence is presented for the presence of different sized Pol delta mRNA's in the asexual and sexual erythrocytic stages of parasite development.

Amino Acid Sequence↗
PubMed1991

A stage specific gene expressed at the onset of gametocytogenesis in Plasmodium falciparum.

The gene encoding the gametocyte specific cytoplasmic protein Pfg27/25 of the human malaria parasite Plasmodium falciparum has been cloned. The gene encodes a highly hydrophilic non-repetitive protein which does not share obvious homologies with other polypeptides. The stage specificity of Pfg27/25 is controlled at the stage of the production of stable mRNA, which is detectable only in the sexual stages of the parasite, and contains long additional sequences outside the Pfg27/25 coding region. As the activation of Pfg27/25 gene expression occurs at an early stage of gametocytogenesis, the study of its regulation might provide information on the molecular events occurring after the parasite commitment to sexual differentiation and at the beginning of gametocyte formation.

Amino Acid Sequence↗
PubMed1991

Plasmodium sexual stage antigens.

The sexual stages of the malaria parasite are highly specialized cells adapted to withstand major environmental changes during their development. They also induce immune responses that may affect the outcome of the infection in the mosquito. In this review Pietro Alano considers the nature and the role of the antigens expressed by Plasmodium sexual stages.

Journal Article↗
PubMed1990

Expression of alpha and beta tubulin genes during the asexual and sexual blood stages of Plasmodium falciparum.

Malaria parasites switch to sexual development after a period of vegetative growth in the host's erythrocytes. This switch, vital for parasite transmission to mosquitoes, is little understood at the genetic level. Likely candidates for developmental control are the alpha- and beta-tubulin subunits required for microtubule assembly. We report here that the transcription of the alpha- and beta-tubulin genes in Plasmodium falciparum show a radically different pattern of transcription in the sexual and sexual phases of parasite growth. Our studies lead to the conclusion that three transcripts of the beta-tubulin gene differ by sequences in their 5'- or 3'-untranslated regions.

Animals↗
PubMed1990

Commitment of the malaria parasite Plasmodium falciparum to sexual and asexual development.

Blood-stage malaria parasites in the vertebrate host can develop either into the asexual, multiplying forms, called schizonts, or into gametocytes, the sexual stages of the parasite. In the present work we studied the differentiation into asexual parasites or gametocytes of the progeny of single, isolated schizonts of the clone 3D7A of Plasmodium falciparum, using monoclonal antibodies specific for the sexual or asexual stages of the parasite. We observed that schizonts obtained from a continuous culture undergoing serial cycles of growth and dilution with fresh red blood cells produced either only gametocytes or only asexual parasites, showing a high degree of commitment to one or the other developmental pathway. The relative proportion of schizonts which produced gametocytes was very low at low parasite densities in culture, while at high parasite densities a much greater proportion of schizonts produced gametocytes. Nevertheless, at both low and high parasite densities individual schizonts were almost always fully committed to producing only gametocytes or only asexual parasites.

Animals↗
PubMed1989

Plasmodium falciparum: an abundant stage-specific protein expressed during early gametocyte development.

A stage-specific protein has been identified in gametocytes of Plasmodium falciparum. The protein is represented on two-dimensional electrophoresis by peptides of two apparent Mr of 27,000 and 25,000, each of which has at least four different isoelectric points between pH 6.0 and 5.0. The protein is designated Pfg 27/25 (P. falciparum gametocyte-specific antigen of 27 and 25 kDa). By indirect immunofluorescence with a monoclonal antibody 1H12 specific for Pfg 27/25, this protein is present in gametocytes within 30 to 40 hr after invasion of a red blood cell by a merozoite and is present throughout subsequent maturation of the gametocyte; Pfg 27/25 is not detectable on the surface of extracellular gametes by immunofluorescence with Mab 1H12. Pfg 27/25 is absent from asexual stages of P. falciparum at any stage in their development. Pfg 27/25 is an abundant protein in gametocytes and represents between 5 and 10% of total protein of these stages. Pfg 27/25 is also a major immunogen in man during P. falciparum infection. Antibodies to this protein were readily detected in human sera from an area of holoendemic P. falciparum and also from an individual following a primary attack of P. falciparum.

Animals↗
PubMed1986

Regulation of the plasmid state of the genetic element P4.

After infection of sensitive cells in the absence of a helper phage, the satellite bacteriophage P4 enters a temporary phase of uncommitted replication followed by commitment to either the repressed-integrated condition or the derepressed-high copy number mode of replication. The transient phase and the stable plasmid condition differ from each other in the pattern of protein synthesis, in the rate of P4 DNA replication and in the expression of some gene functions. The regulatory condition characteristic of the P4 plasmid state affects a superinfecting genome, preventing the establishment of the P4 immune condition.

Coliphages↗
PubMed1984

Plasmid mode of propagation of the genetic element P4.

The satellite bacteriophage P4, in the presence of a helper phage, can enter either the lytic or the lysogenic cycle. In the absence of the helper, P4 can integrate in the bacterial chromosome. In addition, the partially immunity-insensitive mutant P4 vir1 can be maintained as a plasmid. We have found that in the absence of the helper, P4 wt also can be maintained as a plasmid, and that both P4 wt and P4 vir1 have two options for their intracellular propagation: a repressed-integrated or a derepressed-high copy number plasmid mode of maintenance. In the repressed mode, the P4 wt genome is only found integrated into the bacterial chromosome, while the P4 vir1 is found also as a low copy number plasmid coexisting with the integrated P4 vir1 genome. The clones carrying P4 in the derepressed-high copy number plasmid state are obtained at low frequency (0.3%) upon infection with P4 wt, while the vir1 mutation increases this frequency about 300-fold. Such clones can be distinguished easily because of their typical colony morphology (rosettes), due to the presence of filamentous cells. Filamentation of the bacterial host suggests that the presence of derepressed P4 genomes in high copy number interferes with the normal cell division mechanism. The derepressed clones are rather stable, but may revert spontaneously to the repressed state. Spontaneous transition from the repressed to the derepressed state was not observed; however, it can be induced by P2 or P4 vir1 superinfection of P4 wt and P4 vir1 lysogens or by growing the P4 vir1 lysogens up to the late exponential phase. The ability of P4 to choose either of two stable states and the potential to shift between these two modes of propagation indicate that the synthesis of the immunity repressor is regulated.

Cloning, Molecular↗