The Securities and Exchange Commission's director of the Division of Trading and Markets is leaving the financial regulator, the SEC has announced. Robert W. Cook will remain in his position on a provisional basis; the SEC did not specify when he would step down, how long that provisional period would last, or indicate who his replacement might be.

The 47-year-old Cook joined the SEC in early 2010 after a stint as partner at the law firm of Clearly Gottlieb Steen & Hamilton. His is the latest in a series of high-level departures from the organization in the wake of current Chairman Mary Schapiro's decision to leave her post. 

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