Article

The yeast RPL9B gene is regulated by modulation between two modes of transcription termination.

Institut Pasteur, Unité de Génétique des Interactions Macromoléculaires, Paris, France.
The EMBO Journal (impact factor: 9.2). 04/2012; 31(10):2427-37. DOI:10.1038/emboj.2012.81 pp.2427-37
Source: PubMed

ABSTRACT RNA Pol II transcription termination can occur by at least two alternative pathways. Cleavage and polyadenylation by the CPF/CF complex precedes mRNA transcription termination, while the Nrd1 complex is involved in transcription termination of non-coding RNAs such as sno/snRNAs or cryptic unstable transcripts. Here we show that transcription of RPL9B, one of the two genes coding for the ribosomal protein Rpl9p, terminates by either of these two pathways. The balance between these two pathways is modulated in response to the RPL9 gene copy number, resulting in the autoregulation of RPL9B gene expression. This autoregulation mechanism requires a conserved potential stem-loop structure very close to the polyadenylation sites. We propose a model in which Rpl9p, when in excess, binds this conserved 3'-UTR structure, negatively interfering with cleavage and polyadenylation to the benefit of the Nrd1-dependent termination pathway, which, being coupled to degradation by the nuclear exosome, results in downregulation of RPL9B gene expression.

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    Article: Nucleolar Trafficking of the Mouse Mammary Tumor Virus Gag Protein Induced by Interaction with Ribosomal Protein L9.
    Andrea R Beyer, Darrin V Bann, Breanna Rice, Ingrid S Pultz, Melissa Kane, Stephen P Goff, Tatyana V Golovkina, Leslie J Parent
    [show abstract] [hide abstract]
    ABSTRACT: The mouse mammary tumor virus (MMTV) Gag protein directs the assembly of immature viral capsids in the cytoplasm, which subsequently bud from the plasma membrane of infected cells. MMTV Gag localizes to discrete cytoplasmic foci in mouse mammary epithelial cells, consistent with the formation of cytosolic capsids. Unexpectedly, we also observed an accumulation of Gag in the nucleoli of infected cells derived from mammary gland tumors. To detect Gag-interacting proteins that might influence its subcellular localization, a yeast-two-hybrid screen was performed. Ribosomal protein L9 (RPL9 or L9), an essential component of the large ribosomal subunit and a putative tumor suppressor, was identified as a Gag binding partner. Overexpression of L9 in cells expressing the MMTV(C3H) provirus resulted in specific, robust accumulation of Gag in nucleoli. Fluorescence resonance energy transfer (FRET) and coimmunoprecipitation analyses demonstrated that Gag and L9 interact within the nucleolus, and the CA domain was the major site of interaction. In addition, the isolated NC domain of Gag localized to the nucleolus, suggesting that it contains a nucleolar localization signal (NoLS). To determine whether L9 plays a role in virus assembly, siRNA-mediated knockdown was performed. Although Gag expression was not reduced with L9 knockdown, virus production was significantly impaired. Thus, our data support the hypothesis that efficient MMTV particle assembly is dependent upon the interaction of Gag and L9 in the nucleolus of infected cells.
    Journal of Virology 11/2012; · 5.40 Impact Factor
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Keywords

conserved 3'-UTR structure
 
conserved potential stem-loop structure
 
CPF/CF complex precedes mRNA transcription termination
 
degradation
 
downregulation
 
non-coding RNAs
 
polyadenylation
 
polyadenylation sites
 
ribosomal protein Rpl9p
 
RNA Pol II transcription termination
 
RPL9 gene copy number
 
RPL9B
 
RPL9B gene expression
 
Rpl9p
 
transcription
 
transcription termination
 
two alternative pathways
 
two genes coding
 
two pathways
 

Rajani Kanth Gudipati