Law firm Williams Mullen has signed a 75,000-square-foot lease to relocate to downtown Raleigh's RBC Plaza.

The building's owner, Raleigh's Highwoods Properties (NYSE: HIW), announced the lease Wednesday. It said the office space in 293,000-square-foot RBC Plaza, which is under construction, is now 95 percent preleased.

Williams Mullen will relocate from Highwoods Tower I in north Raleigh, where the law firm occupies 51,000 square feet. The company plans to move to RBC Plaza in the third quarter of 2009.

"We are excited to be moving to RBC Plaza and the heart of downtown Raleigh," Williams Mullen director Keith Kapp said in a statement. "This is a great opportunity for us to be in a central location in the newest office building in the city. We have been customers of Highwoods for many years and are very pleased to be able to extend this mutually beneficial relationship."

Triangle Business Journal first reported that Williams Mullen was looking to take space in the RBC Plaza.

The RBC Plaza, a 29-story tower that is the tallest building in the Triangle, is scheduled to open this fall with a mix of office, retail and condominium space. All 139 condominiums are under contract with non-refundable deposits, Highwoods says.