Jim Kirk — publisher and editor-in-chief of the Chicago Sun-Times — is departing to join TroncX, which operates the Chicago Tribune, Los Angeles Times and several other national newspapers.

“Jim Kirk has been a critical part of everything good that has happened at the Sun-Times,” Sun-Times Chief Executive Officer Edwin Eisendrath said. “His stellar journalistic values and judgment; his incredible work ethic, and his leadership through very difficult times — these things set him apart as a newsman and as a person.

“The Sun-Times will continue to build on the progress Jim helped bring about. . . . We will continue to deliver great journalism that resonates with the hardworking people of Chicago.”

Kirk is departing for a newly created role at Tronc, short for Tribune Online Content, in which he’ll aim to accelerate the company’s digital growth. His title will be senior vice president of strategic initiatives.

“I’m pleased to join Tronc during a time in the newspaper industry where the business is being reinvented,” Kirk said in a news release.

At the Sun-Times, Managing Editor Chris Fusco will lead the newsroom on an interim basis.

“We are deeply grateful to Jim Kirk for his years of service to the Chicago Sun-Times and wish him success in his future endeavors,” said Jorge Ramirez, board chairman of ST Acquisition Holdings, which acquired Wrapports LLC — parent company of the Sun-Times and Chicago Reader — last month. “Our confidence in Chris Fusco to lead this paper forward as interim editor-in-chief couldn’t be stronger, and we thank him for his willingness to step up in this crucial moment for our paper and for our city.”

An investor group led by Eisendrath and multiple labor organizations, including the Ramirez-led Chicago Federation of Labor, outdueled Tronc to buy the Sun-Times in a bid process overseen by the U.S. Department of Justice.

Though Tronc had vowed to operate the Tribune and Sun-Times as independent titles, media observers had expressed skepticism over how long that might last. The Eisendrath group’s deal preserved two independent newspaper voices in Chicago, one of the last two-newspaper towns in America.