50 Cent, who's made a career calling out flaws in others, lashes out at Interscope head Jimmy Iovine in a new song, "Southside," which also makes fun of Ja Rule's new video, "Uh Oh."

"Think Jimmy Iovine my boss? F*ck Jimmy Iovine! I'm from 134th Street -- I ain't got no motherf*ckin' boss," hollers 50 over the horn-driven track, which was played last night (Aug. 15) on DJ Kay Slay's show on New York radio station Hot 97. It is unlikely the song will appear on 50's new album, "Curtis," due Sept. 11.

In other hip-hop news, Billboard.biz has learned that Young Jeezy and manager Coach K have reunited. Just before the May release of Jeezy's album with his group U.S.D.A., the pair parted way for unknown reasons. Jeezy's longtime friend, Demetrius "Kinky B" Ellerbee, acted as his manager.

"It's great to be working as a team again," says Coach K. "We're looking forward to making his third album bigger and better."

Meanwhile, there are rumblings that rapper the Game is mulling retirement after the release of his next, as-yet-untitled album. 50 Cent and Lupe Fiasco have also hinted at retirement in recent interviews.