Control of microtubule dynamics by the antagonistic activities of XMAP215 and XKCM1 in Xenopus egg extracts

Abstract

Microtubules are dynamic polymers that move stochastically between periods of growth and shrinkage, a property known as dynamic instability. Here, to investigate the mechanisms regulating microtubule dynamics in Xenopus egg extracts, we have cloned the complementary DNA encoding the microtubule-associated protein XMAP215 and investigated the function of the XMAP215 protein. Immunodepletion of XMAP215 indicated that it is a major microtubule-stabilizing factor in Xenopus egg extracts. During interphase, XMAP215 stabilizes microtubules primarily by opposing the activity of the destabilizing factor XKCM1, a member of the kinesin superfamily. These results indicate that microtubule dynamics in Xenopus egg extracts are regulated by a balance between a stabilizing factor, XMAP215, and a destabilizing factor, XKCM1.

Helical Microtubule Arrays and Spiral Growth

“…The effect of MOR1 on microtubule growth is consistent with what is known about its Xenopus relative, XMAP215, which stimulates microtubule polymerization (Vasquez et al, 1994). In animal cells, the stimulatory effect of XMAP215 is antagonized by the central motor kinesin, XKCM1 (Tournebize et al, 2000). According to Hussey and Hawkins (2001), the N-terminal repeat of MOR1 could negate the effect of a destabilizing kinesin, either by binding directly to it or by competing for the microtubule binding site.…”

Aurora B is required for mitotic chromatin-induced phosphorylation of Op18/Stathmin

“…Control or inhibitory MCAK antibody was added 60 min after M phase induction, and chromosomes and spindles were visualized 20 min later. As shown previously (29,50,51), the MCAK antibody prevented formation of a bipolar spindle and, instead, resulted in the formation of large microtubule asters ( Fig. 2A).…”

Expanding the organismal scope of proteomics: Cross‐species protein identification by mass spectrometry and its implications

“…However, using MS and advanced methods of database interrogation, it is becoming increasingly possible to study the proteomes of organisms with unsequenced genomes. Cross-species identifications have been made in these organisms and others not cited: Zea mays [46,47], Pisum sativum [48,49], Papaver somniferum [50], Spinacia oleracea [44], Arabidopsis thaliana [44], Bos taurus [51], Xenopus laevis [30,52], Pichia pastoris [25], and Trypanosoma brucei [28,29]. Many earlier studies utilizing cross-species identification of unknown proteins relied on high mass accuracy MALDI peptide mapping, and therefore may have identified proteins or enzymes highly conserved across the biosphere.…”