NEW YORK — It's official: Michelle Obama is the first lady of American fashion, appearing on the cover of the March issue of Vogue.

Every first lady since Lou Hoover — save Bess Truman — has been featured in the high-fashion magazine, but Obama is only the second to hit the cover.

She appears in a magenta silk sheath dress by Jason Wu, who also designed her inaugural gown.

Vogue editor at large Andre Leon Talley called his interviews with Michelle Obama ahead of the presidential inauguration "one of the best experiences of my life."

"She's so accessible, natural and normal. There's nothing affected about her," he said.

Much of the eight-page feature inside is devoted to Obama's self-described role as "mom in chief" to 10-year-old Malia and 7-year-old Sasha.

Being Vogue, though, the conversation eventually turns to clothes.

"I'm not going to pretend that I don't care about it," Obama said of her wardrobe. "But I also have to be very practical. In the end, someone will always not like what you wear — people just have different tastes."

BILLY JOEL, ELTON TO PLAY CHICAGO

CHICAGO — The Piano Man and the Rocket Man are pairing up for a concert this summer at Chicago's Wrigley Field.

Promoters announced yesterday that Billy Joel and Elton John will play together July 21 at the home of the Chicago Cubs.

The singers-songwriters will perform duets, playing twin pianos and trading vocals. Each will play a set with his own band, followed by both bands joining for a finale.

Joel and John started their hugely successful Face 2 Face concert tours in 1994.

They played together in the Chicago area in 2001 and 2003.

'GREY'S' LOSING IZZIE, GEORGE

LOS ANGELES — "Grey's Anatomy" cast member James Pickens Jr. says the medical drama will be saying goodbye to Katherine Heigl (Izzie) and T.R. Knight (George).

Pickens, who plays Dr. Richard Webber on the ABC series, told Us Weekly magazine that Heigl and Knight are leaving.

Pickens says he wishes Heigl "nothing but the best," the magazine reported online yesterday.

He says his other co-star, Knight, wants to pursue other "career paths."

Publicists for Knight and for series creator Shonda Rhimes would not comment. Knight has long been rumored to have wanted out of his contract. Requests for comment from Heigl's publicist and ABC were not immediately returned.

Heigl starred in the films "Knocked Up" and "27 Dresses," and has another movie, "The Ugly Truth," coming out.

CHRIS BROWN CASE STILL BEING BUILT

LOS ANGELES — A district attorney's spokeswoman says Los Angeles police presented a case against singer Chris Brown, but prosecutors have asked for further investigation.

Spokeswoman Jane Robison did not release information on the nature of the case police presented to prosecutors yesterday.

Police booked Brown on Sunday for investigation of making a criminal threat after a woman accused him of assaulting her the night before the Grammy Awards.

The Los Angeles Times, citing unidentified law enforcement sources, reported that the woman is pop superstar Rihanna, his longtime girlfriend.

Brown is free on $50,000 bail.