Vincenzo Mutolo

Synthesis of ribosomal RNA during sea-urchin development

(1) Labelling experiments in vivo followed by sucrose gradient and base analysis of RNA demonstrate that the synthesis of the rRNA extractable from the cytoplasm is at a very low level before gastrulation. At this stage it undergoes a sharp increase. (2) Evidence is provided for the synthesis of a precursor of the cytoplasmic rRNA. (3) The suggestion is made that the increase of rRNA synthesis is due to a preferential synthesis of this type of RNA with respect to other RNA classes.

Gene expression in sea urchin development

SummaryActinomycin D has been administered for various lengths of time and at various concentrations to developing sea urchin embryos. The results obtained support the following suggestions.(1)The shape of respiratory curve up to the mesenchyme blastula stage is not under direct gene control.(2)The RNA needed for gastrulation seems to be made during the period between early and late blastula.(3)The RNA needed for skeleton differentiation is continously made from some time before early gastrula throughout skeleton growth.(4)The process of development of skeleton is extremely sensitive to actinomycin.ZusammenfassungSeeigelkeime wurden während der Frühentwicklung unterschiedlich mit verschiedenen Konzentrationen von Actinomycin D behandelt. — Die Resultate legen folgende Deutungen nahe:1.Der Verlauf der Atmungskurve steht bis zum Stadium der Mesenchymblastula nicht unter genetischer Kontrolle.2.Die zur Gastrulation benötigte RNS dürfte in der Zeit zwischen früher und später Blastula gebildet werden.3.Die zur Differenzierung des Skeletts benötigte RNS wird im Verlauf des Skelettwachstums gebildet; die Synthese beginnt kurz vor der Gastrulation.4.Der Prozeß der Skelettentwicklung ist gegen Actinomycin extrem empfindlich.

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.

Synthesis of ribosomal RNA during sea urchin development: II. Electrophoretic analysis of nuclear and cytoplasmic RNA's

Abstract The kinetics of in vivo labelling of nuclear and cytoplasmic RNA has been studied by acrylamide gel electrophoresis in sea urchin embryos at the stages of blastula and gastrula. A rapidly labelled and slowly migrating RNA has been detected at both stages. Its specific activity reaches much higher levels in the nucleus than in the cytoplasm, where its decay is slower. The synthesis of a nuclear precursor of ribosomal RNA, particularly at the gastrula stage, is suggested.

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.

Synthesis of rRNA in sea urchin embryos: IV. Maturation of rRNA precursor

Abstract The analysis of nucleolar RNA of sea urchin gastrulae after in vivo labeling with 32 P, [ 3 H]uridine or l -[ Me - 3 H]methionine has revealed two peaks of radioactivity due to RNAs heavier than the mature rRNA, one of about 33 S and 2.58 · 10 6 daltons and the other one of 28 S and 1.58 · 10 6 daltons. Their nucleolar localization, their kinetics of labeling and methylation and their base ratio strongly suggest that the 33 S is the rRNA precursor, which is broken down to a mature 18 S and to a 28 S which slowly matures into 26 S.

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.