commercial mortgage pass-through certificates , series 2007-1 2014during the year ended december 31 , 2007 , the company completed a securitization transaction ( the 201csecuritization 201d ) involving assets related to 5295 broadcast and wireless communications towers ( the 201csecured towers 201d ) owned by two special purpose subsidiaries of the company , through a private offering of $ 1.75 billion of commercial mortgage pass-through certificates , series 2007-1 ( the 201ccertificates 201d )