K. Eng et al., RNG2P, A PROTEIN REQUIRED FOR CYTOKINESIS IN FISSION YEAST, IS A COMPONENT OF THE ACTOMYOSIN RING AND THE SPINDLE POLE BODY, Current biology, 8(11), 1998, pp. 611-621
Background: An actomyosin-based contractile ring plays a pivotal role
in cytokinesis. Despite the identification of many components of the r
ing, the steps involved in its assembly are unknown. The fission yeast
Schizosaccharomyces pombe is an attractive organism in which to study
cytokinesis because its cell cycle has been well characterized; it di
vides by medial fission using an actomyosin ring; and a number of S. p
ombe mutants defective in actomyosin ring assembly have been isolated.
Here, we have characterized one such mutant, rng2. Results: Temperatu
re-sensitive rng2 mutants accumulated F-actin cables in the medial reg
ion of the cell but failed to organize the cables into a ring. In mg2-
null mutants, only a spot-like structure containing F-actin was detect
ed. The mg2(+) gene encodes a protein related to human IQGAP1,a protei
n that binds actin and calmodulin and is a potential effector for the
Rho family of GTPases. Rng2p localized to the actomyosin ring and to t
he spindle pole body (SPB) of interphase and mitotic cells. Localizati
on of Rng2p to the actomyosin ring but not the SPB required F-actin. R
ng2p interacted with calmodulin, a component of the SPB and the actomy
osin ring. The rng2 gene showed genetic interactions with three other
actomyosin ring assembly mutants, cdc4, cdc12, and mg5. Conclusions: T
he S. pombe IQGAP-related protein Rng2p is a component oi the actomyos
in ring and the SPB and is required for actomyosin ring construction f
ollowing assembly of F-actin at the division site. (C) Current Biology
Ltd ISSN 0960-9822.