Final answer:
Sigma factors in bacteria are proteins that allow RNA polymerase to recognize specific promoter elements for transcription initiation. In eukaryotes, multiple transcription factors, including TFIID, are involved in this process, with enhancers also playing a role through protein cofactors.
Step-by-step explanation:
The sigma factors in bacteria are specialized proteins that do not contain catalytic activity of the RNA polymerase but rather play a crucial role in initiating the process of transcription. These factors allow the RNA polymerase to recognize specific promoter elements, such as the TATA box in prokaryotes. By contrast, in eukaryotes, the process is more complex. Rather than a single sigma factor, eukaryotic transcription involves multiple transcription factors forming a pre-initiation complex. Among these, TFIID, which includes the TATA-binding protein (TBP), is essential for recognizing and binding to the TATA box within the promoter region. This subsequently recruits RNA polymerase II and other transcription factors necessary for transcription initiation. Enhancers, which can be located far from the gene they regulate, interact with the transcription initiation complex through DNA bending and the action of protein cofactors to increase transcription efficiency.