According to various media reports this morning, the Steelers and center Maurkice Pouncey have agreed in principle to a five year extension.
https://twitter.com/ProFootballTalk/status/477078744230666240

The exact contract details obviously aren’t available yet, but the initial numbers point towards Pouncey becoming the highest paid center in the NFL, in terms of new money. Preliminary reports indicate that the 5 year extension is worth just over $44 Mil, and includes a $13 Mil signing bonus. With the last year of his rookie deal remaining, it’s six years for just over $48 Mil.

The Browns signed Alex Mack to a 5 year, $42 Mil contract last year matching the Jacksonville Jaguars offer sheet. The Steelers are obviously happy with Pouncey’s knee recovery, and wanted to lock up their star center before he became a free agent next year.