Synthesis of Spindle-Associated Proteins in Early Cleavage

Abstract

Synthesis of mitotic spindle proteins is probably one of the normal preparations for division in higher cells (Mazia, 1961). Not so clear, however, is the situation in early embryonic development. The most widely accepted point of view, based upon several independent lines of evidence, is that the unfertilized egg contains a store of preformed spindle precursors, and that the controlling process is assembly, rather than biosynthetic elaboration, of the working mitotic apparatus (MA). The evidence is very thoroughly reviewed in Mazia's monograph (1961).Protein synthesis begins in sea urchin eggs immediately after fertilization (Nakano and Mon-2 ~ B R I E F

The Mitotic Apparatus

“…The number of cleavages that might be carried out with this preexisting protein is difficult to compute, for, although it is obvious that the the volume of the cells must halve at each division, there is little information on the relation of MA size to cell size in later divisions, and the observation of Harris (12) that later divisions may be anastral adds an additional complication. These questions are also related to the problem of the synthesis of mitotic apparatus proteins, which has been investigated by a number of workers (6,11,32,44), but, until the number of proteins involved in the mitotic apparatus and their roles in its structure are known, the data presented here cannot contribute directly to the solution of this problem.…”

Effets de la puromycine sur la mitose, la synthèse des protéines et celle du DNA au cours de la segmentation de l’oeuf de Batracien

“…Nos propres observations autoradiographiques confirment entièrement la précocité des synthèses protéiques dans les oeufs de Batraciens : la leucine radioactive s'incorpore rapidement dans les protéines, surtout nucléaires, après microinjection. Toutefois, à l'inverse de ce qui a été observé chez l'oursin (Gross et Cousineau, 1963 ;Staflford et Iverson, 1964), nous n'avons pas noté d'incorporation massive de leucine dans les protéines de l'appareil mitotique (fuseau et asters). Les conclusions générales des auteurs (Hultin, 1961 ;Gross et Cousineau, 1963), qui ont travaillé sur les oeufs d'oursin nous paraissent néammoins vahdes pour les oeufs de Batraciens.…”

“…Nos résultats antérieurs (Brachet, 1963; montrant que la puromycine n'affecte pas la segmentation des oeufs de Batraciens sont difficiles à concilier avec ceux qui ont été obtenus dans le cas des oeufs d'oursin : en effet, la puromycine inhibe rapidement leur clivage (Hultin, 1961) et l'autoradiographie montre que la leucine radioactive s'incorpore fortement dans leur appareil mitotique (Gross et Cousineau, 1963;Stafford et Iverson, 1964). Il semble donc que, chez l'oursin, l'édification de l'appareil mitotique demande une synthèse de protéines, sensible à la puromycine, pour se réahser.…”

The Effect of Actinomycin on Regeneration Processes in Amphibians*†

“…Since it has been shown that Actinomycin inhibits the DNA-directed RNA synthesis to a greater extent than DNA replication (Slotnick, 1960;Reich et al, 1961Reich et al, , 1962Hurwitz et al, 1962), a number of studies were undertaken to investigate the influence of this substance on developmental processes (Wolsky & Wolsky, 1961, 1964Brachet & Denis, 1963;Lallier, 1963;Gross & Cousineau 1963, 1964Markman & Runnstrhm, 1963;Gross, 1964, Gross, Malkin & Moyer 1964and others). However, relatively little attention was paid in these studies to ''secondary development," i.e.…”