KICKING off the fall market: A number of office tenants in a range of industries are trolling for spaces well over 100,000 square feet, or are in the midst of renewing.

The largest potential tenant may be law firm Paul, Weiss, Rifkind, Wharton & Garrison, currently ensconced at 1285 Avenue of the Americas.

Its lease expires in 2011, and the Newmark Knight Frank team of Barry Gosin and Moshe Sukenik are leading that search, which may be a renewal.

With the biggest blocks of space available, we’re sure Worldwide Plaza on Eighth Ave. and 49th St., and 11 Times Square will be giving tours.

Law firm Gibson, Dunn & Crutcher was hoping to have a new Boston Properties tower to move into but that deal died in January when Mort Zuckerman‘s real estate investment trust decided to mothball the tower at 55th St. and Eighth Ave. Gibson, Dunn remains at 200 Park Ave. and is still seeking 200,000 feet through Lewis Miller at CB Richard Ellis.

Sesame Television Workshop is also in need of 200,000 feet but is now concentrating on the outer boroughs, sources say. Gosin and Robin Fisher are the NKF leads on this deal, which would be a relocation from the Milstein-owned One Lincoln Square.

Another entertainment firm, Horizon Media, has an NKF team helping to find more than 100,000 feet for a consolidation.

Health insurance firm HealthFirst, which is now split into spaces at 25 Broadway and 123 William St., is looking to consolidate in 150,000 to 180,000 feet.

Daoud Awad of Jones Lang LaSalle is leading the assignment.

The firm may luck out and be able to consolidate at William St. CoStar data shows 175,000 feet now being occupied there by the New York State Liquidation Bureau is being marketed by ownership and the state agency is touring with Peter Hennessy at Jones Lang LaSalle for a slightly smaller space.

Also downtown, law firm Kenyon & Kenyon, which has a lease for more than 200,000 feet expiring at One Broadway, needs some elbow room.

It could end up renewing through Steve Siegal at CB Richard Ellis and simply taking expansion space at 11 Broadway.

Meanwhile, New York Life is browsing in both Midtown south and downtown with A. Mitti Liebersohn of Cushman & Wakefield, as it seeks over 250,000 feet.

Meanwhile, we hear Mizuho Corp. is wrapping up a 170,000-foot renewal at 1251 Ave. of the Americas with Bob Flippen, Doug Lehman and Fred Fackelmayer of CB Richard Ellis.

The brokers either didn’t return calls or wouldn’t comment.

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Durst Fetner Residential has finally closed on its purchase of 1212 Fifth Ave. from Mt. Sinai Medical Center. The all-cash deal, for 120,000 feet with 76 units, “was more than we ever expected,” sighed partner Hal Fetner. He declined to reveal the final tab, though others said it was under $100 million.

The developers are negotiating with the 16-story apartment building’s nine remaining tenants and will start renovation work around them in October. “We are . . .prepared to respect their rights to accommodate them,” he added.

The deal includes overseeing the development of a 32-story rental apartment tower above the mechanical space needed for the hospital’s new labs.

Twenty percent of the units will be designated for lower-income families. While the final deal changed over the course of the two years Jimmy Kuhn, David Noonan and Jennifer Schwartzman of Newmark Knight Frank were the brokers on the sale.

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Omnicom just signed a 100,000-foot renewal on three of its six floors at 200 Varick St.

Designtex also renewed for 25,000 feet while the nonprofit charity:water signed a new lease for 7,800 feet. Lee Feld of Feld Real Estate represented Omnicom, and Alex Jinishian of First Service Williams represented De signtex. Chari ty:water repped itself.

Jeff Gural and NKF colleague Donna Vogel, the leas ing agent for the building, represented the building owners. Asking rent was $37 a foot.

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