We recently showed that the Ca M antagonist calmidazolium chloride reduces nuclear accumulation of various SOX proteins, including SRY, SOX-2, SOX-9, and SOX-10, as well as the nucleosomal binding protein HMGN1 (2).
Intriguingly, the yeast protein Nhp6Ap also possesses a Ca M-dependent, Ran-independent mode of nuclear transport (6), implying a general role for Ca M in the nuclear transport of HMG proteins.
Conclusion: hsc70 is a key mediator of the Ca M-dependent nuclear transport mechanism of SRY.
Significance: hsc70 may mediate nuclear transport of other developmentally important transcription factors.
Assays to confirm the functionality of si RNA to hsc70 (100 n FRAP was performed as described previously (19).
Mechanically perforated HTC cells were used to assess nuclear import of GFP-SRY-HMG wild type and mutant derivatives in conjunction with CLSM (MRC-500; Bio-Rad, Richmond, CA) as described previously (3).si RNA knockdown of hsc70 in intact cells showed similar results, indicating clear dependence upon hsc70 for Ca M-dependent nuclear import.