WASHINGTON (CNN) - In the first signs of a second-term shakeup for the Bush administration, the White House announced Tuesday evening that Attorney General John Ashcroft and Commerce Secretary Don Evans have resigned.

In their resignation letters, Ashcroft said the Justice Department would benefit from new leadership in a second Bush term, while Evans told Bush he thought it was time for Evans to return home to Texas.

Ashcroft, one of the administration's top figures on antiterrorism issues, was also one of its highest-profile and most controversial appointees. His resignation will become effective upon confirmation of a successor, Justice Department officials said.

Ashcroft was treated for gallstone pancreatitis in March, and his recovery kept him out of the office for nearly a month. In his handwritten resignation letter, dated Nov. 2, he told Bush the job has been "both rewarding and depleting."

"I believe that the Department of Justice would be well served by new leadership and fresh inspiration," he said. "I believe that my energies and talents should be directed toward other challenging horizons."

In a statement from the White House, Bush said Ashcroft, a former Missouri senator and governor, "has worked tirelessly to help make our country safer" and "served our nation with honor, distinction, and integrity."

"During his four years at the Department of Justice, John has transformed the department to make combating terrorism the top priority, including making sure our law enforcement officials have the tools they need to disrupt and prevent attacks," Bush said.

Evans, who served as Bush's campaign chairman in 2000, is a longtime friend and one of Bush's closest advisers. In his resignation, dated Tuesday, he congratulated Bush on last week's election results -- but said he concluded "with deep regret that it is time for me to return home."

"It is a blessing to have served America with such an extraordinary leader and a true friend," he said.

In response, Bush called Evans "one of my most trusted friends and advisers" and "a valuable member of my economic team."

"Don has worked to advance economic security and prosperity for all Americans. He has worked steadfastly to make sure America continues to be the best place in the world to do business," the president said.