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Translational repression by a transcriptional elongation factor
H R Wilson1, L Kameyama, J G Zhou
1ABL-Basic Research Program, National Cancer Institute-Frederick Cancer Research and Development Center, Maryland 21702-1201, USA.
Genes & Development
|September 26, 1997
Summary
Bacteriophage lambda N protein, a known transcription regulator, also represses its own gene translation. This dual role requires the same RNA site (NUT), but antitermination and repression mechanisms can be independently affected by mutations.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- Bacteriophage lambda N protein is a classical positive regulator of gene expression.
- N protein facilitates transcription of early phage genes by forming a processive, terminator-resistant complex.
- This complex involves an RNA site (NUT) and host proteins (Nus).
Purpose of the Study:
- To investigate previously unknown regulatory roles of bacteriophage lambda N protein.
- To determine if N protein influences its own gene expression at the translational level.
- To elucidate the relationship between N-mediated antitermination and translational repression.
Main Methods:
- Genetic analysis of bacteriophage lambda N protein function.
- Identification and characterization of mutations in NUT sites and host factors (Nus proteins).
- Assays to measure both antitermination and translational repression activities of N protein.
Main Results:
- Demonstrated that N protein acts as a repressor of its own gene translation.
- Showed that N-dependent translational repression requires the same cis-acting NUT site as antitermination.
- Identified mutations that uncouple antitermination from translational repression, indicating distinct mechanisms.
Conclusions:
- Bacteriophage lambda N protein possesses a novel dual regulatory function: antitermination of transcription and repression of its own translation.
- Both functions depend on the NUT site, but can be mechanistically separated by specific mutations.
- The spatial positioning of the NUT site relative to the target gene is critical for repression.