San Diego ? The parent company of The San Diego Union-Tribune said Wednesday that it agreed to sell its flagship newspaper to a private equity firm for an undisclosed price, a rare vote of confidence in an industry that’s hurting so badly that several other once-prized newspapers have been unable to find buyers.

Copley Press Inc. agreed to sell the dominant newspaper in the nation’s eighth-largest city to Platinum Equity, based in Beverly Hills, Calif., eight months after it put the newspaper on the block. It marks the end of the Copley family’s run in the newspaper business, including 80 years as San Diego’s dominant media company.

Louis Samson, a principal at Platinum Equity, called the newspaper “a good fit.”

“The Union-Tribune is more than a business. It’s an institution in San Diego,” Samson said. “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.”