Myosin‑II heavy chain and formin mediate the targeting of myosin essential light chain to the division site before and during cytokinesis

Mol Biol Cell. 2015 Apr 1;26(7):1211-24. doi: 10.1091/mbc.E14-09-1363. Epub 2015 Jan 28.


MLC1 is a haploinsufficient gene encoding the essential light chain for Myo1, the sole myosin‑II heavy chain in the budding yeast Saccharomyces cerevisiae. Mlc1 defines an essential hub that coordinates actomyosin ring function, membrane trafficking, and septum formation during cytokinesis by binding to IQGAP, myosin‑II, and myosin‑V. However, the mechanism of how Mlc1 is targeted to the division site during the cell cycle remains unsolved. By constructing a GFP‑tagged MLC1 under its own promoter control and using quantitative live‑cell imaging coupled with yeast mutants, we found that septin ring and actin filaments mediate the targeting of Mlc1 to the division site before and during cytokinesis, respectively. Both mechanisms contribute to and are collectively required for the accumulation of Mlc1 at the division site during cytokinesis. We also found that Myo1 plays a major role in the septin‑dependent Mlc1 localization before cytokinesis, whereas the formin Bni1 plays a major role in the actin filament-dependent Mlc1 localization during cytokinesis. Such a two‑tiered mechanism for Mlc1 localization is presumably required for the ordered assembly and robustness of cytokinesis machinery and is likely conserved across species.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / metabolism
  • Cell Division / physiology*
  • Cytokinesis / physiology*
  • Cytoskeletal Proteins / metabolism
  • Microfilament Proteins / metabolism*
  • Myosin Heavy Chains / metabolism*
  • Myosin Light Chains / metabolism*
  • Protein Transport
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Septins / metabolism


  • BNR1 protein, S cerevisiae
  • Bni1 protein, S cerevisiae
  • Cytoskeletal Proteins
  • MLC1 protein, S cerevisiae
  • MYO1 protein, S cerevisiae
  • Microfilament Proteins
  • Myosin Light Chains
  • Saccharomyces cerevisiae Proteins
  • Septins
  • Myosin Heavy Chains