Kirkland & Ellis is advising private equity firms The Blackstone Group and Madison Dearborn Partners on a pair of major transactions announced Monday.

In the larger of the two deals, Kirkland—which dominated the buyout rankings of legal advisers for the year’s first quarter—is counseling Madison Dearborn on its proposed $6.25 billion sale of Nuveen Investments to the New York–based Teachers Insurance and Annuity Association–College Retirement Equities Fund Company. If completed, the acquisition will make TIAA-CREF one of the nation’s largest money managers.

Kirkland corporate partners Richard Porter, Neal Reenan, Michael Snow and Steve Toth, investment management partner Scott Moehrke and associates Kevin Bettsteller and Aisha Lavinier are advising Chicago-based Nuveen and Madison Dearborn on the sale, which includes about $4.6 billion in Nuveen debt and is expected to close by year’s end. (Porter, who has long been active in the Republican Party, was named earlier this year to serve as Illinois’ representative on the GOP’s national committee.)

A frequent Kirkland client, Madison Dearborn turned to the firm in 2013 for counsel on both its $1.6 billion buy of hospital therapy provider Ikaria and its $1.75 billion sale of The Yankee Candle Company, according to our previous reports. An SEC filing shows the firm also reaped a portion of the $875,000 in legal fees and expenses generated by Madison Dearborn portfolio company Boise Cascade’s $247.1 million initial public offering last year.

Skadden, Arps, Slate, Meagher & Flom investment management partner Michael Hoffman and counsel Kevin Hardy and financial institutions regulation and enforcement head William Sweet Jr. and counsel James Frazer are advising Nuveen, along with financial institutions cohead David Hepp and Chicago tax group leader David Polster, both of whom are advising on equity compensation matters. Skadden served as regulatory counsel to Nuveen back in 2007 on its $6.4 billion going-private transaction, one that Fortune reports has finally paid off for Madison Dearborn.

Also representing Nuveen on its current sale are Winston & Strawn corporate partner Steven Gavin, employee benefits partner Erin Kartheiser and labor and employment chair Rex Sessions. Winston is also counseling Nuveen’s management. Former Winston partner John MacCarthy, who joined Nuveen as general counsel in 2006, is leading an in-house team at the asset manager that includes managing director Kevin McCarthy and assistant general counsel William Means Jr. and Christopher Rohrbacher.

Gresham Investment Management, a boutique portfolio manager that turned to Schulte Roth & Zabel for counsel on the sale of a majority stake to Nuveen in late 2011, is being advised in connection with Nuveen’s current sale to TIAA-CREF by Schulte M&A partner Christopher Harrison, bank regulatory partner Joseph Vitale and associate Lane Verlenden. Adam Gehrie serves as Gresham’s chief compliance officer and general counsel.

William Forgione, a senior managing director and general counsel for asset management at TIAA-CREF, is leading his own in-house team working on the Nuveen deal that includes senior director and associate general counsel Keith Atkinson and directors and associate general counsel Dennis Machado, John McCally, John McCann and Michael Phillips. TIAA-CREF hired former Wilmer Cutler Pickering Hale and Dorr partner and broker-dealer practice chair Brandon Becker as its chief legal officer in 2009.

William Regner, cohead of Debevoise & Plimpton’s M&A group, is leading a team from the firm serving as outside counsel to TIAA-CREF on the matter. Other Debevoise attorneys working on the deal include investment management partner Kenneth Berman, executive compensation chair Lawrence Cagney and tax partner Peter Schuur.

U.S. Senate lobbying records show that TIAA-CREF paid Patton Boggs $20,000 in 2013 for work on insurance company taxation issues as well as issues related to oversight of insurers and their products. Washington, D.C.’s Davis & Harman received $70,000 for lobbying on TIAA-CREF’s behalf in connection with tax incentives for retirement savings. Madison Dearborn’s Nuveen, meanwhile, paid Hogan Lovells another $320,000 last year to lobby on issues related to municipal bond tax exclusion, according to Senate filings.

In the second of Monday’s two major private equity deals in which Kirkland played a lead role, the firm advised The Blackstone Group on its joint acquisition with Goldman Sachs’ merchant banking arm of capital markets software provider Ipreo Holdings from fellow private equity firm KKR.

M&A partners David Fox and Daniel Wolf—both of whom joined Kirkland in 2009 from Skadden—are leading the firm’s team advising Blackstone. Other Kirkland lawyers working on the matter include corporate partner Leo Greenberg, debt finance partners Jay Ptashek and Eric Wedel and associates Andrew Glickman and Meredith Waters.

One of Blackstone’s top firms for transactional work, Simpson Thacher & Bartlett, is representing New York–based KKR in this instance. Simpson corporate partners—and seasoned KKR dealmakers—Mark Pflug and Gary Horowitz are advising the buyout giant, along with capital markets partner James Cross, employee benefits partners David Rubinsky and Andrea Wahlquist and tax partner Nancy Mehlman.

While the terms of the deal were not disclosed, various news reports pegged the value at $957 million. Ipreo hired former Bank of America/Merrill Lynch in-house lawyer Ben Sherwin as its general counsel in early 2012. Former Simpson executive committee member David Sorkin serves as KKR’s general counsel, while ex–Simpson global M&A head John Finley is a senior managing director and chief legal officer at Blackstone.

For counsel on its end of the Ipreo deal, Goldman’s merchant banking unit is relying on Fried, Frank, Harris, Shriver & Jacobson finance head F. William Reindel and Davis Polk Wardwell to provide outside legal counsel. (Former Goldman deputy general counsel David Greenwald left the financial services giant last year to join Fried, Frank, Harris, Shriver & Jacobson, where he has since been installed as chair. Gregory Palm, a former Sullivan & Crowell partner, is Goldman’s general counsel.)

Senate records show that Goldman paid Nixon Peabody $240,000 last year to lobby on financial services regulatory and tax issues and doled out another $480,000 to Patton Boggs affiliate the Breaux Lott Leadership Group to advise on Dodd-Frank Act and Consumer Protection Act matters. Senate filings also show that KKR paid Akin Gump Strauss Hauer & Feld’s $600,000 last year to lobby on “public policy issues affecting private equity firms and their portfolio companies.”