Final answer:
Trans-acting elements in eukaryotes are typically transcription factors, which are proteins that bind to DNA sequences to regulate gene expression. These elements function at a distance from their target genes and are essential for the initiation of transcription by RNA polymerase II.
Step-by-step explanation:
The question refers to trans-acting elements, which are factors that can function at a distance from their target genes within eukaryotic cells. In the context of eukaryotic transcription, these trans-acting elements are typically transcription factors, which are proteins that bind to specific DNA sequences to control the transcription of genes.
Transcription initiation in eukaryotes requires the action of RNA polymerase II alongside several transcription factors that bind to complex promoter sequences. For example, the initiation involves the TATA-binding protein that recognizes the TATA box within the promoter region, as well as other transcription factors binding to additional sequences like the CAAT box and GC box.
Overall, the term 'trans-acting element' refers to various transcription factors in eukaryotes that regulate gene expression by binding to specific promoter sequences across the genome, rather than being directly adjacent to the gene they regulate. This differentiates them from cis-acting elements, which are DNA sequences in the immediate vicinity of the region of the DNA being transcribed.