FIG. 1.

Identification of HSP90-HSF1 heterocomplexes in Xenopus oocyte nuclei. (A) Immunoblot showing subcellular distribution of HSP90. Oocytes were incubated at a nonshock (NS) temperature (18°C) or heat shocked (HS) at 33°C for 2 h, and proteins from single intact oocytes or from the nuclear and cytoplasmic fractions were separated by SDS-PAGE along with purified bovine HSP90 as a control. HSP90 was detected with an HSP90 PAb. The positions of molecular mass standards are shown on the left. (B) Coimmunoprecipitation of HSF1 and HSP90 from oocyte nuclei. HSF1 and YY1 were immunoprecipitated with rabbit anti-mouse HSF1 PAb (55) or YY1 PAb (Santa Cruz). Nuclear extracts were isolated from nonshocked or heat-shocked (33°C for 1 h) oocytes. Immunoprecipitated material was subjected to SDS-PAGE and transferred to nitrocellulose, and the blot was probed with HSP90 and HSF1 Abs as indicated.