The regulatory light chain of nonmuscle myosin is encoded by spaghetti-squash, a gene required for cytokinesis in Drosophila.
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.
Karess
R E
RE
Department of Biochemistry, NYU Medical Center, New York 10016.
Chang
X J
XJ
Edwards
K A
KA
Kulkarni
S
S
Aguilera
I
I
Kiehart
D P
DP
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002455:Cell Division; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004331:Drosophila melanogaster / Q000235:genetics*; D015870:Gene Expression; D005796:Genes; D008938:Mitosis; D008969:Molecular Sequence Data; D009154:Mutation; D009218:Myosins / Q000235:genetics* / Q000502:physiology; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping; D014158:Transcription, Genetic
D012333:RNA, Messenger; D009218:Myosins