Bipartite function of a small RNA hairpin in transcription antitermination in bacteriophage lambda
| Autor: | Samit Chattopadhyay, Jaime García-Mena, Asis Das, Joseph DeVito, Krystyna Wolska |
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| Jazyk: | angličtina |
| Rok vydání: | 1995 |
| Předmět: |
Small RNA
Genes Viral Transcription Genetic Molecular Sequence Data Biology Substrate Specificity chemistry.chemical_compound Bacterial Proteins Transcription (biology) RNA polymerase Escherichia coli Viral Regulatory and Accessory Proteins Binding site Cloning Molecular Promoter Regions Genetic Transcription factor Genetics Multidisciplinary Binding Sites Base Sequence Models Genetic Escherichia coli Proteins RNA DNA-Directed RNA Polymerases Peptide Elongation Factors Bacteriophage lambda Cell biology Transcription antitermination chemistry Oligodeoxyribonucleotides Antitermination Mutagenesis Site-Directed Nucleic Acid Conformation RNA Viral Transcriptional Elongation Factors Research Article Transcription Factors |
| Popis: | Transcription of downstream genes in the early operons of phage lambda requires a promoter-proximal element known as nut. This site acts in cis in the form of RNA to assemble a transcription antitermination complex which is composed of lambda N protein and at least four host factors. The nut-site RNA contains a small stem-loop structure called boxB. Here, we show that boxB RNA binds to N protein with high affinity and specificity. While N binding is confined to the 5' subdomain of the stem-loop, specific N recognition relies on both an intact stem-loop structure and two critical nucleotides in the pentamer loop. Substitutions of these nucleotides affect both N binding and antitermination. Remarkably, substitutions of other loop nucleotides also diminish antitermination in vivo, yet they have no detectable effect on N binding in vitro. These 3' loop mutants fail to support antitermination in a minimal system with RNA polymerase (RNAP), N, and the host factor NusA. Furthermore, the ability of NusA to stimulate the formation of the RNAP-boxB-N complex is diminished with these mutants. Hence, we suggest that boxB RNA performs two critical functions in antitermination. First, boxB binds to N and secures it near RNAP to enhance their interaction, presumably by increasing the local concentration of N. Second, boxB cooperates with NusA, most likely to bring N and RNAP in close contact and transform RNAP to the termination-resistant state. |
| Databáze: | OpenAIRE |
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