Constitutive hsp70 is essential to mitosis during early cleavage of Paracentrotus lividus embryos: The blockage of constitutive hsp70 impairs mitosis

Localization of constitutive hsp70 in eggs and early embryos of sea urchin Paracentrotus lividus is shown by means of in situ immunostaining. An accum ulation of this protein is shown in the mitotic structures (asters, spindle s and centrosomes). Microinjection of anti-hsp70 antibodies into eggs cause s impairment of formation of mitotic structures and of cell division. This impairment goes from a complete mitotic block, to irregular mitotic apparat us formation with irregular cleavage, depending upon the antibody concentra tion. The localization of hsp70 after antibody microinjection is also descr ibed. Blockage of mitotic apparatus formation by nocodazole also blocks the concentration of hsp70 molecules observed in nontreated eggs. That the con stitutive hsp70 plays a role in sea urchin mitosis is indicated. (C) 1999 A cademic Press.