[ by Howard Haykin ] A senior Wall Street regulator will step down in September, ending a nearly 2-decade career, as her agency undergoes a makeover.  Considered one of banking's most powerful, yet polarizing regulators, Julie Williams – chief counsel of the Office of the Comptroller of the Currency – announced on Monday that she would leave the agency on 9/30/12.  Ms. Williams, also twice served as acting comptroller. Ms. Williams, who typically worked behind the scenes in Washington ... is a skilled lawyer with a mastery of esoteric financial minutiae - which helped position to herself as the go-to adviser.  In recent months, she's led the agency's effort to write new rules for Wall Street and played a role in dissecting the multi-billion dollar trading loss at JPMorgan Chase. Yet, her policies rubbed some Congressional Democrats the wrong way, and they depicted her as a sympathetic regulator with a light touch.  She fought to temper crucial aspects of the Dodd-Frank regulatory overhaul law, according to people briefed on the matter, and beat back efforts to afford state regulators greater authority over banks. In recent years, some lawmakers tried to curb her significant power over the state of financial regulation.  For example, an early version of Dodd-Frank stripped her OCC position of its civil service status, which serves to protect government employees from being fired.  The wording was removed from the final version of the law. Concurrent Agency Overhaul. Her departure coincides with a recent overhaul of the agency, the national banking regulator long criticized as too cozy with the industry it oversees.  Thomas Curry, a former FDIC director who's known for taking a critical eye to Wall Street, took over the Office of the Comptroller of the Currency in April.  He then hired Paul Nash, a senior FDIC official, as his chief of staff.  It is Mr. Curry's arrival that many view as the main factor for Ms. Williams' departure. Big Law Awaits. Some people at the agency expect her to land a job in the financial industry, though Ms. Williams has yet to publicly identify her next step.  A move to the private sector would end nearly 30 years of regulatory work.  Before joining the OCC in 1993, she worked at 2 now-extinct financial regulators: the FHLBB and the Office of Thrift Supervision. For further details, go to:    [Dealbook, 8/13/12].