Beverly Hills private equity firm Platinum Equity announced Wednesday it will buy the San Diego Union-Tribune for an undisclosed price.

As declining circulation and advertising revenue has decimated the newspaper industry, Copley Press Inc., based in La Jolla, put the newspaper up for sale in July 2008. The deal is expected to close in the second quarter.

Platinum, founded in 1995 by Tom Gores, specializes in acquiring and resuscitating businesses facing operational challenges. The firm has completed nearly 100 deals in a range of industries.

“We have a long history of creating value by helping established companies navigate difficult market transitions,” Louis Samson, the Platinum principal in charge of the transaction, said in a statement. “The Union-Tribune is more than a business, it’s an institution in San Diego. But it faces enormous challenge in a period of tremendous upheaval for the newspaper industry. We will bring a strong operational focus that helps ensure the Union-Tribune not only survives in this market, but thrives.”

The purchase comes as other newspaper markets in the United States face big changes. This week, the Seattle Post-Intelligencer ended print operations after its owner, Hearst Corp., failed to find a buyer for the newspaper. The move followed the complete shutdown in late February of Denver’s Rocky Mountain News, which owner E.W. Scripps & Co. was unable to sell.