Ernst & Young signed a 10-year lease for 203,618 square feet at The John Buck Co.'s new office development at 155 N. Wacker Drive in Chicago's West Loop. This latest deal, which is one of the largest downtown office leases this year, brings the 1.13 million-square-foot building to 72 percent preleased. Completion of the 46-story high-rise is slated for next summer.