Does Reg E apply to DBA accounts?

If by "DBA account" you mean a business account of a sole proprietor, the answer is "No." For transactions to be covered by Regulation E, they have to pass a couple of tests. First, the account has to held by a natural person. A sole prop clearly fits that test. Second, the account has to be opened and maintained primarily for personal, family, or household use. A sole prop business account flunks that test.