The House Committee on Oversight deposed Karl Rove's former assistant, Susan Ralston.   A pdf version of transcript of the deposition can be found at The Gavel [1].  In this morning's  Washington Post [2], an article on this White House e-mail scandal reported Ms. Ralston's revelation that Karl Rove frequently used RNC e-mail accounts, and not his White House account:

Former Rove assistant Susan B. Ralston affirmed in a deposition released by the committee that her ex-boss used his political e-mail account "most of the time."

The White House previously acknowledged that aides to President Bush improperly used the political e-mail accounts. But the material released yesterday details for the first time how frequently they used the accounts and for what purposes.

The committee said it learned that the White House aides used the RNC accounts to discuss official matters such as appointments and grant announcements. It also said at least 88 White House officials had RNC e-mail accounts, a figure above previous administration statements that only about 50 had such accounts.