In Gram-positive quorum sensing, such as that observed for Staphylococcus aureus, RNA III regulates expression by coding for a

Question

BlackTom AI · Accepted Answer

RNA III is a regulatory antisense RNA produced from the agr P3 transcript in Staphylococcus aureus and functions by base-pairing with target mRNAs to control their translation and stability.

1) Relevant knowledge points and concepts
- Gram-positive quorum sensing in S. aureus uses the agr locus (agrBDCA and promoters P2/P3). Accumulated autoinducing peptide (AIP) activates the AgrC/AgrA two‑component system.
- Activated AgrA drives transcription from P3, producing RNAIII (~514 nt), the primary effector of the agr regulon.
- Antisense RNAs are noncoding (or primarily noncoding) RNAs that regulate gene expression by complementary base pairing with target mRNAs, altering translation initiation or mRNA stability.

2) Step-by-step reasoning
- Step 1: agr operon senses cell density via AIP → AgrC/AgrA activation.
- Step 2: AgrA upregulates the P3 promoter → synthesis of RNAIII.
- Step 3: RNAIII interacts by complementary base pairing with specific mRNAs (for example, spa mRNA encoding protein A and rot mRNA encoding a repressor), blocking ribosome binding or altering mRNA structure.
- Step 4: These interactions either repress translation or expose ribosome binding sites to activate translation (e.g., modulating hla expression), thereby changing virulence gene expression.

3) Intermediate molecular steps (examples)
- RNAIII base pairs with the 5′ UTR of spa mRNA → prevents ribosome binding → reduced protein A production.
- RNAIII disrupts inhibitory secondary structure of hla mRNA → increases alpha-toxin translation.

4) Why "Antisense RNA" is correct
RNAIII functions primarily through sequence-specific antisense interactions with target mRNAs rather than by encoding a regulatory protein. Its regulatory effects arise from base-pairing-mediated modulation of translation and mRNA stability, the defining mechanism of an antisense RNA.

5) Why other options are incorrect
- A protein transcription factor: RNAIII does not act chiefly by encoding a regulatory protein (although it contains a short ORF for δ-hemolysin, its regulatory role is RNA-mediated).
- A riboswitch: riboswitches are cis-acting metabolite-sensing elements in untranslated regions, not trans-acting regulatory RNAs like RNAIII.
- microRNA: miRNAs are eukaryotic small RNAs processed by Dicer; bacterial RNAIII is a different bacterial antisense sRNA.

6) Conclusion
Because RNAIII controls target gene expression via complementary base pairing and translational control, it is an antisense RNA. This confirms the provided correct answer: Antisense RNA.

In Gram-positive quorum sensing, such as that observed for Staphylococcus aureus, RNA III regulates expression by coding for a单项选择题

类似问题

A mutation occurs in the quorum sensing regulation pathway of Vibrio fischeri in which the activated LuxR protein cannot bind to the lux operon. This mutation would cause the lux operon to:

In Staphylococcus aureus, a mutation prevents AgrC from phosphorylating AgrA, but all other parts of the system are functional. Which of the following is the most likely income at high cell density?

Match organism/process with function: 1: Streptomyces 2: Vibrio fischeri 3: Pseudomonas spp. 4: Burkholderia spp. 5: E. coli

Which of the following is TRUE of quorum sensing?

During biofilm formation, increased quorum sensing enables bacteria to _____________

Question at position 8 An excess of growth hormone (GH) before puberty can result in the development ofgigantism.Graves' disease.acromegaly.pituitary dwarfism.Clear my selection

Question at position 6 The most abundant supporting cells in the central nervous system are called Question Blank 1 of 1[input].

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单