Rng2p, a protein required for cytokinesis in fission yeast, is a component of the actomyosin ring and the spindle pole body.
BACKGROUND
An actomyosin-based contractile ring plays a pivotal role in cytokinesis. Despite the identification of many components of the ring, 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 divides by medial fission using an actomyosin ring; and a number of S. pombe mutants defective in actomyosin ring assembly have been isolated. Here, we have characterized one such mutant, rng2.


RESULTS
Temperature-sensitive rng2 mutants accumulated F-actin cables in the medial region of the cell but failed to organize the cables into a ring. In rng2-null mutants, only a spot-like structure containing F-actin was detected. The rng2+ gene encodes a protein related to human IQGAP1, a protein that binds actin and calmodulin and is a potential effector for the Rho family of GTPases. Rng2p localized to the actomyosin ring and to the spindle pole body (SPB) of interphase and mitotic cells. Localization of Rng2p to the actomyosin ring but not the SPB required F-actin. Rng2p interacted with calmodulin, a component of the SPB and the actomyosin ring. The rng2 gene showed genetic interactions with three other actomyosin ring assembly mutants, cdc4, cdc12, and rng5.


CONCLUSIONS
The S. pombe IQGAP-related protein Rng2p is a component of the actomyosin ring and the SPB and is required for actomyosin ring construction following assembly of F-actin at the division site.
Eng
K
K
Cell Division Laboratory, Institute of Molecular Agrobiology, National University of Singapore.
Naqvi
N I
NI
Wong
K C
KC
Balasubramanian
M K
MK
D000205:Actomyosin / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D001483:Base Sequence; D002147:Calmodulin / Q000502:physiology; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology; D017931:DNA Primers / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D020690:GTPase-Activating Proteins; D005800:Genes, Fungal; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology* / Q000235:genetics / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid; D008941:Spindle Apparatus / Q000502:physiology
D002147:Calmodulin; D018797:Cell Cycle Proteins; D017931:DNA Primers; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D008164:Luminescent Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; C114172:Rng2 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D049452:Green Fluorescent Proteins; D000205:Actomyosin