Anna Maria Pirrone

Synthesis of ribosomal RNA in disaggregated cells of sea urchin embryos

Abstract The specific activity of the α-phosphate of the acid-soluble nucleotide pool has been found to remain constant for several hours after the dissociation into cells of embryos previously exposed to inorganic 32 P. The rate of incorporation of 32 P into 28-S rRNA of dissociated cells deriving from prelabeled embryos has been used as a measure of the rate of rRNA synthesis. The results strongly suggest that neither intercellular contact nor cell division, at least from the stage of hatching on, are needed for the activation of rRNA synthesis, characteristic of the normal development, to take place.

Synthesis of ribosomal RNA during sea urchin development: III. Evidence for an activation of transcription

Abstract Embryos of Paracentrotus lividus have been preloaded with 32P1 until the early blastula stage. The amount of the total acid-soluble nucleotide pool, as well as the specific activity of the α-phosphates of such nucleotides, were found to remain practically constant until at least the prism stage. The specific activity attained at different stages by the 28-S rRNA was calculated and referred to the total DNA content of the embryos. An activation of rRNA transcription following the swimming blastula stage has been demonstrated.

Chromosomal Location of Ribosomal DNA (rDNA), (GATA)n and (TTAGGG)n Telomeric Repeats in the Neogastropod Fasciolaria Lignaria (Mollusca: Prosobranchia)

This paper reports on a successful application of fluorescent in situhybridization (FISH) with three repetitive DNA probes (ribosomal DNA (rDNA), (GATA)nand (TTAGGG)n) in the chromosomes of Fasciolaria lignaria(Mollusca: Prosobranchia: Neogastropoda). rDNA FISH consistently identified four chromosome pairs per spread in the three examined specimens. The telomeric sequence (TTAGGG)nhybridized with termini of all chromosomes. GATA FISH revealed abundant, dispersed minisatellite regions which were not associated to the XY sex-determining mechanism as indicated by the absence of a Y specific pattern of labelling.

Effect of chemical animalization and vegetalization on the synthesis of ribosomal RNA in sea urchin embryos

SummaryTreatment of embryos of Paracentrotus lividus with a concentration of ZnSO4 which causes animalization, strongly inhibits the initiation of ribosomal RNA synthesis.The vegetalizing agent LiCl does not seem clearly to affect the synthesis of this RNA.ZusammenfassungIn mit ZnSO4 animalisierten Embryonen von Paracentrotus lividus ist der Beginn der ribosomalen RNS-Synthese stark gehemmt.Das vegetalisierende LiCl scheint nicht die Synthese dieser RNS zu beeinflussen.

Physical mapping of rDNA genes, (TTAGGG)n telomeric sequence and other karyological features in two earthworms of the family Lumbricidae Annelida: Oligochaeta)

A cytogenetical study was carried out on the chromosomes and nuclear DNA amounts of the terrestrial earthworms Octodrilus complanatus and Eisenia foetida (Annelida: Oligochaeta: Lumbricidae). Chromosomes were studied using Giemsa staining, banding methods and fluorescent in situ hybridization (FISH) with two repetitive DNA probes [rDNA and (TTAGGG)n]. rDNA FISH and silver staining consistently identified one chromosome pair per spread in both species. The telomeric sequence (TTAGGG)n hybridized with termini of all the chromosomes in both earthworms. Flow cytometry DNA assays showed that O. complanatus and E. foetida had different nuclear DNA contents (2C value=1.72 and=1.40 pg, respectively) but very similar base composition in their genomes.

Studies on the regulation of ribosomal RNA synthesis in sea urchin development.

Abstract Cells of sea urchin hatching blastulae and gastrulae when reaggregated together do not influence each other with respect to the rate of rRNA synthesis. Extracts from unfertilized eggs and embryos inhibited rRNA synthesis by gastrulae. However, the inhibition was equally strong with extracts from stages that have a low rate of rRNA synthesis (eggs, cleavage embryos) as with extracts from stages that have a high rate of rRNA synthesis (oocytes, gastrulae). Synthesis of ppGpp is not detected at any of the investigated developmental stages.

Maturational cleavage of nucleolar ribosomal RNA precursor can be catalyzed by non-specific endonuclease

Abstract A cell-free system has been developed that allows incubation of prelabeled oocyte nucleoli, with no spontaneous processing of the 32-S rRNA precursor. It is shown that the addition of a nuclear lysate of embryos, of a stage that in vivo shows a fast rRNA maturation, causes the specific cleavage of the 32-S rRNA precursor into the 27-S and 21-S products. This specific cleavage can also be induced by the addition of a non-specific endonuclease such as the bovine pancreatic ribonuclease. Specific cleavage of the purified 32-S RNA with pancreatic RNAase is much more difficult to achieve. It is inferred that the nucleolar proteins protect the 32-S rRNA precursor from the endonuclease attack, leaving it much more exposed at the site where it has to be cut for the maturational processing.

Analysis of exogenous P32 incorporation into the nucleotidic pool of sea urchin embryos

I t has been shown in a previous paper (Sconzo et al., 1970a) t h a t when fertilized Paracentrotus lividus eggs are exposed to exogenous p3~ for 8 hours, the la t ter becomes incorporated into the nucleotidic pool and tha t the specific ac t iv i ty of the e-phosphates of the nucleotides remains cons tant a t least for fur ther 16 hours. This knowledge enables one to calculate from the a m o u n t of radioac t iv i ty t ransferred wi th in 8 and 24 hours after fert i l izat ion from the pool to accumula t ing RNAs (e.g. ribosomal) the ne t synthesis of RN A in terms of moles. A l imit to this calculat ion was however represented by the possibil i ty t ha t the ac t iv i ty of the e-phosphates in nucleotides monoand di-phosphates was different from tha t of the t r iphosphates and t h a t this difference changed as development proceeded. We have therefore unde r t aken a detai led analysis of the ex ten t of labeling of several nueleotides. This analysis is also of a pract ical value when one considers t h a t the so labeled nucleotidic pool of the sea urch in embryo represents a convenien t source of t r iphosphate nueleotides labeled in the e-phosphate t ha t can be used as substrates for in vitro nucleic acid synthesis.

Synthesis of RNA in isolated nuclei of sea urchin embryos

SummaryIt is demonstrated that isolated nuclei of sea urchin embryos are able to incorporate radioactive nucleotides into RNA.Some properties of the incorporation system are described.