Jeannemarie joined Wachtell, Lipton, Rosen & Katz in 1997 and was elected partner in 2003. She focuses on executive compensation and benefits aspects of transactions, with a particular focus on representing commercial and investment banks, thrifts and financial service institutions. Ms O'Brien also advises companies on compensatory arrangements in both the public and private sectors, as well as compensation-related corporate governance issues, and has extensive experience in advising financial institutions receiving assistance from the U.S. government.

In 2008, Chambers USA recognized Jeannemarie as a leader in Employee Benefits. She has played a role in mergers and acquisitions totaling more than $500 billion in deal value over the course of the past decade, and has represented numerous companies in the most noteworthy transactions in the financial sector. These representations include:

• Wells Fargo & Company in its acquisition of Wachovia Corporation
• Bank of America Corporation in its acquisitions of Merrill Lynch and Countrywide Financial
• JPMorgan Chase in several transactions, including its acquisition of The Bear Stearns Companies and the exchange of its corporate trust business for the banking arm of The Bank of New York
• North Fork Bancorporation in its acquisition by Capital One Financial Corp.
• Golden West Financial Corporation in its acquisition by Wachovia Corporation
• FleetBoston Financial Corporation in its merger with Bank of America
• Bank One in its $58 billion merger with JPMorgan Chase
• Household International, Inc. in its acquisition by HSBC Holdings plc
• American International Group Inc. in its $24 billion acquisition of American General
• Wasserstein Perella Group Inc. in its cross-border merger with Dresdner Bank AG
• Fleet Financial Group Inc. in its $15 billion merger with BankBoston Corp.

• Wells Fargo in its merger with Norwest Corp.

Jeannemarie also advises companies outside the financial sector. Most recently, she represented Longs Drug Stores in its announced acquisition by CVS Caremark, UAP Holding Corp. in its acquisition by Agrium, Inc. and Dollar General Corporation in its acquisition by Kohlberg Kravis Roberts & Co. She advised Apollo Management, L.P. in its acquisitions of Harrah’s Entertainment Inc. and Realogy Corporation, as well as Home Depot in its 2007 stock sale to a group of private equity buyers. Moreover, Jeannemarie represented Valero Energy Corp. in both its merger with Premcor Inc. and its acquisition of Ultramar Diamond Shamrock Corp.

In addition to representing leading companies in their critical transactions, Jeannemarie frequently writes memoranda and articles that discuss key issues and developments in executive compensation. Each year, she contributes a chapter to "Financial Institutions M&A," an annual review of current topics written by a small group of partners focused on transactions in the financial sector.

Jeannemarie received a B.A. in Political Science and Italian in 1989 from Mt. Holyoke College, where she graduated cum laude. She received her J.D. from Fordham Law in 1994 and was Associate Editor of Fordham Law Review. Before joining the team at Wachtell, Lipton, Rosen & Katz, Jeannemarie worked as an associate at Dewey Ballantine.