Standard & Poor's will add Celgene ( CELG) to its S&P 500 index to replace AmSouth Bancorp ( ASO).

Regions Financial ( RF) is acquiring AmSouth in a deal expected to close by Nov. 6.

Regions, in turn, will supplant RadioShack ( RSH) in the S&P 100, Standard & Poor's said Monday.

RadioShack, with a market capitalization of about $2.4 billion, ranked 100th in the S&P 100 as of the close of trading Monday.

The moves will occur after the close of trading Nov. 3.

Shares of Celgene, a biotech company, climbed $2.15, or 4.3%, to $52 in after-hours trading. Shares of companies added to the S&P 500 often rise because fund managers who track the index have to own the shares.

If you liked this article you might like

Spain to Play Netherlands for World Cup

Spain to Play Netherlands for World Cup

Wal-Mart: Analysts' Upgrades, Downgrades

Wal-Mart: Analysts' Upgrades, Downgrades

Netherlands Advances to World Cup Final

Netherlands Advances to World Cup Final

Apple: Analysts' Upgrades, Downgrades

Apple: Analysts' Upgrades, Downgrades

World Markets Mostly Lower Monday

World Markets Mostly Lower Monday