The regulatory light chain of nonmuscle myosin is encoded by spaghetti-squash, a gene required for cytokinesis in Drosophila

• Published in: Cell Vol. 65; no. 7; p. 1177
• Main Authors: Karess, R E, Chang, X J, Edwards, K A, Kulkarni, S, Aguilera, I, Kiehart, D P
• Format: Journal Article
• Language: English
• Published: United States 28-06-1991
• Subjects: Alleles; Amino Acid Sequence; Animals; Base Sequence; Blotting, Northern; Blotting, Southern; Cell Division; Chromosome Mapping; Cloning, Molecular; Drosophila melanogaster - genetics; Gene Expression; Genes; Mitosis; Molecular Sequence Data; Mutation; Myosins - genetics; Myosins - physiology; Nucleic Acid Hybridization; Phenotype; Restriction Mapping; RNA, Messenger - genetics; Transcription, Genetic
• ISSN: 0092-8674
• DOI: 10.1016/0092-8674(91)90013-O

Two independent approaches to understanding the molecular mechanism of cytokinesis have converged on the gene spaghetti-squash (sqh). A genetic screen for mitotic mutants identified sqh1, a mutation that disrupts cytokinesis, which was then cloned by transposon tagging. Independently, the gene that encodes the regulatory light chain of the biochemically defined nonmuscle myosin (MRLC-C) was also cloned. We show here that sqh encodes MRLC-C and that in sqh1 mutants, the level of stable light chain transcript is greatly reduced. Reversion by transposon excision or transformation with a wild-type copy of the sqh transcription unit rescues cytokinesis failure and other defects in sqh1. Vertebrate homologs of MRLC-C are phosphorylatable and regulate myosin activity in vitro. These studies provide genetic proof that MRLC-C is required for cytokinesis, suggest a role for the protein in regulating contractile ring function, and establish a genetic system to evaluate its function.