Cell cycle‐dependent association of Gag‐Mil and hsp90

Abstract
Immunoprecipitated p100Gag‐Mil protein kinase from MH2‐transformed quail embryo fibroblasts is associated with an 89 kDa protein. The molar ratio between p89 and Gag‐Mil in the immunocomplex is 0.72, indicating that the majority of Gag‐Mil is complexed with p89. During mitosis part of Gag‐Mil is shifted to a form with reduced electrophoretic mobility, p102Gag‐Mil. Appearance of p102Gag‐Mil leads to a reduced association with p89 indicating that p102 is not associated with p89. Microsequencing of p89 isolated from immunoprecipitates of Gag‐Mil identified the protein as the quail homologue of chicken hsp90. Our results show that p100Gag‐Mil is associated with hsp90 with a high stoichiometry and that upshifted p102Gag‐Mil is released from the complex with hsp90.