CHICAGOBoston-based American Tower Corp. has purchased the top four floors and the roof of the John Hancock Center here for a reported $70 million.

The acquisition of the physical space, along with the existing telecommunications leases, is another move toward the vertical subdivision of the tower, the fourth-tallest building in Chicago and the sixth-tallest in the United States. Deutsche Bank A.G. and NorthStar Realty Finance Corp. are reportedly selling off portions of the 100-story tower after the building was defaulted earlier this year. The tower totals about 2.8 million sq. ft.

Steve Marshall, executive vice president and president of the company’s U.S. tower division, said this transaction allows American Tower to make a prominent entrance into the Chicago-area broadcast market, while augmenting its rooftop portfolio in the region. The agreement includes more than 34,000 sq. ft. of space for broadcast and telecommunications equipment, the rooftop and two broadcast masts.

“Our experience in supporting the broadcast and wireless industries makes us a prime partner for both existing as well as new tenants at the property,” he said in a statement. “American Tower continues to pursue opportunities to grow our portfolio through the acquisition and development of rooftop assets suitable for assisting our tenants in optimizing their networks.”

He said the company will begin marketing the property to both broadcast and wireless tenants, given the site’s extensive capacity for collocation. The space is ready for collocation and installation and features ready-to-build infrastructure, multiple fiber connections and two megawatts of on-site backup power.