Nippon Steel Corp., Japan's largest steel production company, announced Monday morning that it will acquire Pittsburgh-based US Steel in an all-cash deal, valued at $55 per share, which equates to more than 2 trillion yen or about $14 billion.

At $55 in cash, the deal is a 40% premium to the closing price of US Steel shares on Friday. Shares of X are up 27% in premarket trading in New York, around $50 a share.