Billionaire Sam Zell has joined a slate of board nominees for CommonWealth REIT, the U.S. office landlord being targeted by an investor group seeking to overthrow the company’s management.

Zell and David Helfand, co-president of Zell’s Equity Group Investments, will join the proposed slate of directors to be nominated at a special meeting of CommonWealth shareholders if the current board is removed, according to a statement today from investors Corvex Management LP and Related Cos. They are seeking to replace the trustees based on claims of mismanagement and conflicts of interest.

Zell and Helfand are willing to serve as CommonWealth’s chairman and chief executive officer, respectively, Corvex and Related said.