As recently as 2010, Jack Lew, President Obama‘s nominee to be the next secretary of the Treasury, had $56,000 invested in a CitiGroup venture capital fund based in the Cayman Islands’ notorious Ugland House, a building whose mailboxes are home to nearly 19,000 corporate entities, many of them tax shelters.The investment has been in public documents for years and drew no attention when Mr. Lew was confirmed to be deputy secretary of state in 2009 and director of the White House Office of Management and Budget in 2010.But the fund is coming to light as Mr. Obama and Congressional...