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Published on: October 4, 2018
5S ribosomal RNA is an essential component of a nascent ribosomal precursor complex that regulates the Hdm2-p53
Giulio Donati1, Suresh Peddigari, Carol A Mercer
1Laboratory of Cancer Metabolism, ICO/IDIBELL, Hospital Duran i Reynals, Gran Via de l'Hospitalet, 199-08908 Hospitalet de Llobregat, Barcelona, Spain.
Abstract:
Recently, we demonstrated that RPL5 and RPL11 act in a mutually dependent manner to inhibit Hdm2 and stabilize p53 following impaired ribosome biogenesis. Given that RPL5 and RPL11 form a preribosomal complex with noncoding 5S ribosomal RNA (rRNA) and the three have been implicated in the p53 response, we reasoned they may be part of an Hdm2-inhibitory complex. Here, we show that small interfering RNAs directed against 5S rRNA have no effect on total or nascent levels of the noncoding rRNA, though they prevent the reported Hdm4 inhibition of p53. To achieve efficient inhibition of 5S rRNA synthesis, we targeted TFIIIA, a specific RNA polymerase III cofactor, which, like depletion of either RPL5 or RPL11, did not induce p53. Instead, 5S rRNA acts in a dependent manner with RPL5 and RPL11 to inhibit Hdm2 and stabilize p53. Moreover, depletion of any one of the three components abolished the binding of the other two to Hdm2, explaining their common dependence. Finally, we demonstrate that the RPL5/RPL11/5S rRNA preribosomal complex is redirected from assembly into nascent 60S ribosomes to Hdm2 inhibition as a consequence of impaired ribosome biogenesis. Thus, the activation of the Hdm2-inhibitory complex is not a passive but a regulated event, whose potential role in tumor suppression has been recently noted.
Insights
Ribosome proteins RPL5 and RPL11, along with 5S rRNA, form a complex that inhibits Hdm2 and stabilizes p53. This complex redirects from ribosome assembly to Hdm2 inhibition when ribosome biogenesis is impaired, acting as a regulated tumor suppressor.
Area of Science:
- Molecular Biology
- Cellular Biology
- Cancer Research
Background:
- Ribosome biogenesis is crucial for cell growth and proliferation.
- Impaired ribosome biogenesis can trigger cellular stress responses.
- The p53 tumor suppressor pathway is often activated by cellular stress.
Purpose of the Study:
- To investigate the role of 5S ribosomal RNA (rRNA) in the p53 response.
- To determine if 5S rRNA forms a complex with RPL5 and RPL11 to inhibit Hdm2.
- To elucidate the regulation of the Hdm2-inhibitory complex in response to impaired ribosome biogenesis.
Main Methods:
- ব্যবহার করা হয়েছে small interfering RNAs (siRNAs) to target 5S rRNA and TFIIIA.
- Depletion of RPL5 and RPL11 was performed.
- Co-immunoprecipitation assays were used to assess protein-Hdm2 binding.
Main Results:
- Depletion of 5S rRNA did not affect its total or nascent levels but prevented Hdm4 inhibition of p53.
- Targeting TFIIIA or depleting RPL5/RPL11 did not induce p53.
- 5S rRNA, RPL5, and RPL11 function dependently to inhibit Hdm2 and stabilize p53.
- Depletion of any component disrupted the binding of the others to Hdm2.
- The RPL5/RPL11/5S rRNA complex is redirected from 60S ribosome assembly to Hdm2 inhibition upon impaired ribosome biogenesis.
Conclusions:
- 5S rRNA is essential for the Hdm2-inhibitory function of the RPL5/RPL11 complex.
- The activation of this Hdm2-inhibitory complex is a regulated event, not passive.
- This regulated complex plays a role in tumor suppression.
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