RESTON, Va. (AP) — An investor group led by private equity firm Siris Capital Group is buying data communications company TNS for $516.6 million.

Siris will pay $21 a piece for each TNS Inc. share. This is a 44 percent premium to TNS's Monday closing stock price of $14.56. The companies said that the total value of the transaction is about $862 million.

Shares of TNS jumped $6.26, or 43 percent, to $20.82 on Tuesday. The stock has traded in a 52-week range of $13.59 to $22.84.

TNS currently has approximately 24.6 million outstanding shares according to FactSet. The company is allowed to seek out alternative third-party buyout proposals for a 30 day period.

The deal, which was unanimously approved by TNS's board, is expected to close in 2013's first quarter.