text: The process of activation and binding in eukaryotes is different from bacteria in the way that specific DNA elements bind the factors for a functional pre-initiation complex. In bacteria there is a single polymerase, that contain catalytic subunits and a single regulatory  subunits known as sigma, which transcribe for different type of genes.
  In eukaryotes, the transcription is performed by three different RNA polymerase, RNA pol I for ribosomal RNAs (rRNAs), RNA polymerase II for messenger RNAs (mRNAs) and some small regulatory RNAs, and the RNA polymerase III for small RNAs such as transfer RNAs (tRNAs). The process of positioning of the RNA polymerase II and the transcriptional machinery require the recognition of a region known as "core promoter". The elements that could be found in the core promoter include the TATA element, the TFIIB recognition element (BRE), the initiator (Inr), and  the downstream core promoter element (DPE). Promoters in eukaryotes contain one or more of these core promotes elements (but any of them are absolutely essential for promoter function), these elements are binding sites for subunits of the transcriptional machinery and are involve in the initiation of the transcription, but also they have some specific enhancer functions. In addition, the promoter activity in eukaryotes include some complexities in the way of how they integrate signals from distal factors  with the core promoter.