Update (9:42 a.m. EST): In its formal statement, News Corporation (News International's parent company) didn't give a clear reason why James Murdoch was leaving. It said he was moving to New York to "assume a variety of essential corporate leadership mandates, with particular focus on important pay-TV businesses and broader international operations." It also noted that Tom Mockridge, News International's CEO, would take over the U.K. publishing arm. But it seems pretty clear to the outside observer that James Murdoch resigned as a result of the U.K. Leveson inquiry into press ethics, where he appeared out of touch with his operation as the British government investigated phone hacking and bribery allegations at now-shuttered News of the World and the newly expanded Sun. In November, while James Murdoch testified before a parliamentary committee last November, one member of Parliament, Tom Watson, compared News International to the Mafia. He famously quipped to Murdoch, "You must be the first Mafia boss in history who didn't know he was running a criminal enterprise." 

The Guardian posted the full text of News Corp.'s announcement of Murdoch's change in duties:

News Corporation today announced that, following his relocation to the company's headquarters in New York, James Murdoch, deputy chief operating officer, has relinquished his position as executive chairman of News International, its UK publishing unit. Tom Mockridge, chief executive officer of News International, will continue in his post and will report to News Corporation president and COO Chase Carey.

"We are all grateful for James' leadership at News International and across Europe and Asia, where he has made lasting contributions to the group's strategy in paid digital content and its efforts to improve and enhance governance programs," said Rupert Murdoch, chairman and chief executive officer, News Corporation. "He has demonstrated leadership and continues to create great value at Star TV, Sky Deutschland, Sky Italia, and BSkyB. Now that he has moved to New York, James will continue to assume a variety of essential corporate leadership mandates, with particular focus on important pay-TV businesses and broader international operations."

"I deeply appreciate the dedication of my many talented colleagues at News International who work tirelessly to inform the public and am confident about the tremendous momentum we have achieved under the leadership of my father and Tom Mockridge," said James Murdoch. "With the successful launch of the Sun on Sunday and new business practices in place across all titles, News International is now in a strong position to build on its successes in the future. As deputy chief operating Officer, I look forward to expanding my commitment to News Corporation's international television businesses and other key initiatives across the company."

Original: James Murdoch, the son of News Corporation owner Rupert Murdoch, has just stepped down as executive chairman of the company, the Associated Press reports, and will focus instead on "global TV ventures," tweets NPR media correspondent David Folkenflik.