Draw a bacterial promoter and label its consensus sequences. How does this promoter differ from a eukaryotic promoter transcribed by RNA polymerase II? By RNA polymerase I? By RNA polymerase III?

Key Concepts

Bacterial Promoter Structure

A bacterial promoter is a specific DNA sequence that initiates transcription in prokaryotes. It typically contains consensus sequences such as the -10 (Pribnow box) and -35 regions, which are recognized by RNA polymerase. These sequences are crucial for the binding of the transcription machinery and the subsequent initiation of RNA synthesis.

Eukaryotic Promoter Variability

Eukaryotic promoters are more complex than bacterial promoters and can vary significantly between different genes. They often include a TATA box, initiator elements, and other regulatory sequences that are recognized by RNA polymerase II. This complexity allows for precise regulation of gene expression in response to various cellular signals.

RNA Polymerase Types in Eukaryotes

Eukaryotic cells contain three main types of RNA polymerases: RNA polymerase I, II, and III, each responsible for transcribing different classes of genes. RNA polymerase I primarily transcribes ribosomal RNA (rRNA), RNA polymerase II transcribes messenger RNA (mRNA) and some snRNA, while RNA polymerase III transcribes tRNA and other small RNAs. Each polymerase interacts with distinct promoter elements, reflecting their specialized roles in gene expression.