RESUMO
Function of condensin subunits XCAP-E and pEg7 (XCAP-D2) in the formation and maintaining of special organization of mitotic chromosomes has been studied in Xenopus laevis cells (XL-2). The experimental conditions involved blocking chromosomes being in the condensed state in cells treated by cytostatics, or during their reversible artificial decondensation. The latter was induced by incubation of living cells in hypotonic medium. In extensively mollen chromosomes, XCAP-E and pEg7, remained associated with axial regions of chromosomes. In contrast, upon adaptation of cells to hypotonic conditions and recondensation of chromosomes to nearly initial state, both proteins dissociated from chromosomes into the cytoplasm. In K-mitotic cells, after a 3-6 h treatment with nocodazole or taxol, considerable dissociation of XCAP-E and pEg7 from chromosomes was observed without significant changes in overall level of chromosome compactization. Taken together the data suggested that condensins play no important role in maintaining mitotic chromosomes being in condensed state. Rather, it seems probable that mitotic function of condensins may be associated either with the formation of the higher order chromosome structure, and/or segregation of sister chromatids, the processes being tightly linked with chromosome compactization. This paper is in memory of Professor Katherine Le Guellec of Rennes-1 University, who left us in June 2001. Professor Le Guellec initiated this work in Rennes and offered all the possible help that this work be continued in Moscow University. Let the memory of Katherine, a great scientist and sympathetic friend, live for ever in ours hearts.
