In eukaryotic genes, promoters are located [ Select ] ["surrounding the transcription start site", "surrounding the transcription termination site", "always in the first intron", "just about anywhere within a million bases of the gene"] where they are bound by [ Select ] ["transcription factors", "general transcription factors", "ribosomes", "Xrn2"] ; enhancers are located [ Select ] ["surrounding the transcription start site", "surrounding the transcription termination site", "always in the first intron", "just about anywhere within a million bases of the gene"] where they are bound by