Question

Which of the following statements is TRUE regarding eukaryotic RNA polymerases (I, II, and III)?

A) The core promoter for RNA polymerase I is internal to the transcribed region.
B) All have the same subunits.
C) RNA polymerase III has a heptad (7) amino acid repeat at its C-terminus (CTD).
D) Only RNA polymerase II works with TBP.
E) All work with TBP at the promoter.

Answer 1

Answer: Among the statements provided, the true statement regarding eukaryotic RNA polymerases (I, II, and III) is:

C) RNA polymerase III has a heptad (7) amino acid repeat at its C-terminus (CTD).

Step-by-step explanation:

1. RNA polymerase I: The core promoter for RNA polymerase I is not internal to the transcribed region, making statement A incorrect. RNA polymerase I transcribes ribosomal RNA (rRNA) genes, which are located in the nucleolus of eukaryotic cells. The core promoter for RNA polymerase I is located upstream of the transcription start site.

2. Subunits: All three eukaryotic RNA polymerases (I, II, and III) do not have the same subunits, making statement B incorrect. While they share some common subunits, each RNA polymerase has its own unique set of subunits that contribute to their specific functions and regulation.

3. RNA polymerase III: This RNA polymerase is responsible for transcribing small noncoding RNAs, including transfer RNA (tRNA) genes. RNA polymerase III has a heptad (7) amino acid repeat at its C-terminus (CTD), making statement C true. The CTD of RNA polymerase III is involved in the assembly of transcription complexes and the interaction with transcription factors.

4. RNA polymerase II: This RNA polymerase transcribes protein-coding genes and some noncoding RNAs. It works with the TATA-binding protein (TBP) and other transcription factors at the promoter region. Therefore, statement D is incorrect as RNA polymerase II, not only works with TBP but also interacts with other transcription factors.

5. TBP and promoter: While RNA polymerase II specifically interacts with the TATA-binding protein (TBP), statement E is incorrect because not all eukaryotic RNA polymerases work with TBP at the promoter. RNA polymerase I and RNA polymerase III have their own unique promoter elements and interact with different transcription factors.

In summary, the true statement regarding eukaryotic RNA polymerases (I, II, and III) is that RNA polymerase III has a heptad (7) amino acid repeat at its C-terminus (CTD).