Study of the Link between Translation Termination and Ribosome Biogenesis
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Release factor 1 (RF1) is a ribosome-binding protein required for termination of translation in Escherichia coli. To study the effect of slow termination on protein synthesis, two isolated suppressors to a temperature sensitive (Ts) mutant allele of RF1 were studied. The first mutation, rpsIt2215, located within the transcription terminator for the rplM operon, affects expression of ribosomal protein S9. This protein is part of the head domain of the small ribosomal subunit and facilitates mRNA accommodation during translation initiation. The second mutation is a small deletion of the initiation region of gene rimN. rimN141 leads to no production of functional protein, which in wild type is essential for 16S rRNA maturation. Still, even though the RimN protein contains a dsRNA-binding surface, it does not bind tightly to the ribosome. RimN’s probable function in 16S rRNA processing is to resolve and refold intermediate rRNA structures.
Both rpsIt2215 and rimN141 affect maturation of 30S ribosomal subunit. The defect can be observed as a decrease in the amount of translating ribosomes, and as shown in the case of rimN141, also induced expression of rRNA. The affected 30S assembly and translation initiation might be part of the mutant RF1 suppression mechanism, acting through increased cellular RF1 concentrations or a decreased requirement for efficient termination.
Not much is known about how the expression of RF1 is regulated. RF1 is encoded by the prfA gene, located as the second gene in the hemA operon. Three promoters have been suggested to regulate its transcription. Two of them, promoters P1hemA and P2hemA, are located upstream of hemA, the first gene in the operon. P1hemA is the stronger promoter and has been suggested to be regulated upon changes in growth rate and (p)ppGpp concentrations. However, our results do not support this view. The third promoter, PprfA, is putative and the +1 start site of transcription is located to the hemA-coding region.
Place, publisher, year, edition, pages
Stockholm: Institutionen för genetik, mikrobiologi och toxikologi , 2004. , 62 p.
IdentifiersURN: urn:nbn:se:su:diva-288ISBN: 91-7265-961-0OAI: oai:DiVA.org:su-288DiVA: diva2:192000
2004-12-09, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 10:00
Squires, Catherine L., Professor
Rydén Aulin, Monica, Docent
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