Greene and Zhong  established that infection by C. trachomatis affects host cell cytokinesis in a multipliCity of infection-dependent manner, results that were confirmed in our work (Fig. 1). Grieshaber et al.  demonstrated that chlamydial inclusions associate with the centrosome leading to increased numbers of centrosomes and chromosome segregation defects in infected cells. Molecular interactions
between chlamydiae and host ABT-888 in vitro molecules important in cell division were explored by Balsara et al.  who showed that chlamydial infection leads to alterations in the abundance of cyclin-dependent kinases and to the cleavage of cyclin B1. However, any chlamydial proteins that might participate in the alteration of the host cell cycle have not been identified. While it is possible that the observed multinuclear phenotype is a function of cellular fusion, as opposed to inhibition of cytokinesis, Greene and Zhong  discuss several lines of evidence that point to the latter possibility. This includes the lack of observed fusion intermediates, the presence of mitotic forms, and normal DNA synthesis in chlamydiae-infected host cells. These observations support the likelihood that cells are being blocked in a terminal State of division, as opposed to being stimulated to fusion with neighboring cells, following chlamydial infection. CT223p was first examined
as a candidate selleck kinase inhibitor Inc protein because of the presence of an amino-terminal bi-lobed hydrophobic domain that is proposed to be a membrane anchor for Incs . Like many Incs, CT223p also contains
a long carboxy-terminal tail that is largely hydrophilic. It is likely that this carboxy-terminal region of the protein is responsible for direct interactions between Incs and Fossariinae proteins in the host cell cytosol, a property shown to be true for tested Inc proteins [7, 21, 22]. Transfection of cells with plasmids encoding only the carboxy-terminal 179 amino acids or (to a lesser extent) the 56 carboxy-terminal amino acids of CT223p led to increased accumulation of host cell nuclei within cells. We have sequence data for CT223p from several C. trachomatis isolates and, while there is sequence variation among strains, the carboxy-terminal third of the protein is highly conserved [; data not shown]. Two other Inc proteins, CT224p and CT225p, also affected host cell cytokinesis, although the effect was less than that observed with CT223p. These proteins are encoded sequentially in the C. trachomatis genome and are unique to this species. However, the predicted protein sequences of these three proteins share very limited primary amino acid identity. In contrast, the protein product of C. muridarum orf TC0495, an apparent homolog of CT223 that is encoded in a syntenous operon  did not block cytokinesis in our assays.