There is evidence for the association of M1 with lipid rafts in influenza infected cells, whereas M1 expressed alone remains soluble (Ali et al., 2000; Zhang and Lamb, 1996), suggesting association of M1 with other viral proteins in targetting to the cell membrane. Coexpression of HA and NA together with M1 has been shown to promote raft association of M1. This association requires the TMD and cytoplasmic tails of HA and NA (Ali et al, 2000; Zhang et al, 2000). This is consistent with M1 becoming associated with HA and NA during their passage through the exocytic pathway to raft domains in the apical membrane. alternatively M1 may use the cytoskeleton to reach the virus assembly site, as M1 interacts with cytoskeletal components (Alvalos et al., 1997). The M1 interaction depends on the presence of RNP and is most likely mediated by direct binding of F-actin by NP (Digard et al., 1999).