Association of the Anillin‐related Protein Mid1 With Actin

Abstract

Schizosaccharyomyces pombe, like human cells, divide symmetrically through constriction of an acto‐myosin ring. The conserved protein Mid1 plays a key role in the early assembly of the ring. Cells lacking mid1 form acto‐myosin rings that are non‐centered and disorganized, resulting in unequal division of the cellular contents. In human cells a Mid1 related protein called anillin regulates contraction of this ring. Anillin contains an actin binding domain that is necessary for the protein's direct association with actin. Unlike anillin, Mid1 does not contain an actin binding domain, and its ability to interact directly with actin has not been previously reported. However, previous studies show that anillin depleted and Mid1 depleted cells show similar defects in ring placement, ring formation, and cytokinesis. To assess whether or not Mid1 directly associates with actin, in vitro actin binding assays were performed. To further characterize the relationship between Mid1 and the acto‐myosin ring, we tested the ability of actin to bind GST‐Mid1 fragments with and without targeted mutations. Determining which members of the acto‐myosin ring associate directly with actin, an essential ring component, will provide significant insight into the molecular details of cytokinesis.Research supported by NSF‐Advance and GVSU.