Bonnie Fuller (search) is going downmarket.

The fast-moving editor-in-chief who turned Us Weekly into a newsstand juggernaut is quitting to become editorial director at supermarket tabloid publisher American Media, home to the National Enquirer, Star, as well as Shape and Muscle & Fitness, sources said.

She also stands to be the highest paid editor in the publishing world, topping Norman Pearlstine (search) at Time Inc. and Vanity Fair's Graydon Carter (search).

Under the deal with American Media she could make up to $3 million a year, but that figure is heavily weighted to dramatic circulation gains.

Fuller will now team up with American Media CEO David Pecker, a corporate wheeler dealer who, like Fuller, has always been seen as something of an outsider by the chattering media elite in the Big Apple.

At American Media, tabloid veteran Steve Coz will now report to Fuller, making her the highest ranking editorial executive in the company.

The sudden move stunned Rolling Stone founder Jann Wenner (search), who heads Wenner Media, which owns Us Weekly in partnership with Walt Disney.

"I'm shocked," said Wenner, who in February had reported reaching a new three-year agreement with the superstar editor who had rescued the floundering title and turned it into a profitable magazine with circulation over 1.1 million.

Asked if he did indeed have a three-year contract, Wenner said, "I thought we did."

One source explained that while they had an agreement in principle, she never signed the papers. "She never signed anything and they never locked her in," the source said.

That deal with Wenner was reportedly for $1 million per year.

Wenner said he has not ruled out legal action. "That's something for the lawyers to look at," he said. "I don't know if we would."

Wenner said she broke the news to him in a 10-minute conversation yesterday afternoon and did not disclose her new destination.

"I'm sorry about it," he said. "I think she's a terrific editor and she was doing a terrific job."

Fuller could not be reached.

Last fall, Fuller was named Ad Age's Editor of the Year and her momentum showed no signs of slowing.

Wenner told staffers he would have a new editor in chief at the helm of US very shortly. Janice Min, executive editor and one of the members of "Bonnie's Posse" was cutting short a vacation in Europe to return to New York. Insiders said they expected her to be offered the top job.

Pecker has been aggressively trying to build American Media.

He closed his $350 million deal for Weider Publications earlier this year. More recently, only three years after dumping most of the Tarrytown, N.Y., staff of Star Magazine to bring it to Boca Raton, Florida, he reversed course and decided to bring the publication back to the Big Apple, where it was started in the 1970s.

He had been conducting a series of interviews to find a new editor-in-chief. He could not be reached at press time.