Yahoo Inc. is nearly doubling its office space at Santa Monica’s Colorado Center in a lease deal valued at $80 million, according to sources close to the agreement.

The Internet company will sublease 150,000 square feet being abandoned by Metro-Goldwyn-Meyer Inc., and take another 64,000 square feet of soon-to-be-vacant space.

Assuming 10-year leases at market-rate rents of roughly $3.10 a foot, the additional 214,000 square feet could be worth $79.6 million to the center’s owners, Equity Office Properties and pension fund TIAA-CREF.

Equity Office spokeswoman Paige Steers declined to comment, as did Gerald Porter, vice chairman with Cresa Partners, which is representing Yahoo in the deal. Calls to Yahoo weren’t returned.

Earlier this year, Yahoo inked leases for up to 256,000 square feet at the campus-like office complex in a deal valued at up to $100 million.

Yahoo moved several related divisions from its headquarters in Sunnyvale to be closer to Hollywood studios and dealmakers. By November 2007, the company will occupy nearly 470,000 square feet, or 43 percent, of the 1.1 million-square-foot Colorado Center.

The deal with Yahoo ensures that Colorado Center, which is being renamed Yahoo Center, will be largely occupied for the foreseeable future. That’s good news for the Equity Office/TIAA-CREF partnership that purchased the 1.1 million-square-foot complex last year from Tishman Speyer Properties Inc. for $443.6 million.

Before Yahoo stepped in, the owners of Colorado Center were facing large vacancies.

MGM, which was bought earlier this year by a group led by Sony Corp., stationed its home video division at the property, which had also been the studio’s headquarters before the company moved to Century City in 2003.