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

Cell. 1991 Jun 28;65(7):1177-89. 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 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
  • RNA, Messenger / genetics
  • Restriction Mapping
  • Transcription, Genetic


  • RNA, Messenger
  • Myosins

Associated data

  • GENBANK/M59201
  • GENBANK/M63700
  • GENBANK/M63702
  • GENBANK/M63718
  • GENBANK/M67494
  • GENBANK/S40357
  • GENBANK/S63145
  • GENBANK/S63146
  • GENBANK/S63147
  • GENBANK/S63148