Warren Buffett’s Berkshire Hathaway has spent another $54 million to purchase Sirius XM stock, giving it a stake of more than 35% in the satellite-radio company.

Or, at least someone on his investment team is. Buffett's holding company now owns around $2.4 billion in Sirius XM shares, equal to roughly 30% of the total shares outstanding. Buffett's involvement alone is triggering many investors to pay closer attention.

Warren Buffett’s Berkshire Hathaway (BRK.A) (BRK.B) has recently increased its stake in Sirius XM Holdings Inc. (SIRI), now owning over 35% of