TY - JOUR
T1 - Novel role of nucleostemin in the maintenance of nucleolar architecture and integrity of small nucleolar ribonucleoproteins and the telomerase complex
AU - Romanova, Liudmila
AU - Kellner, Steven
AU - Katoku-Kikyo, Nobuko
AU - Kikyo, Nobuaki
PY - 2009/9/25
Y1 - 2009/9/25
N2 - Nucleostemin (NS) is a nucleolar protein involved in the regulation of cell proliferation. Both overexpression and knock-down ofNSincrease the activity of the tumor suppressor protein p53, resulting in cell cycle arrest. In addition, NS regulates processing of pre-rRNA and consequently the level of total protein synthesis. Here, we describe a previously uncharacterized function of NS in the maintenance of the tripartite nucleolar structure as well as the integrity of small nucleolar ribonucleoproteins (snoRNPs). NS is also necessary to maintain the telomerase complex which shares common protein subunits with the H/ ACA box snoRNPs. First, immunofluorescence microscopy and electron microscopy demonstrated that knockdown of NS disorganized the nucleolar architecture, in particular, the dense fibrillar component where snoRNPs are localized. Second, gel filtration chromatography and immunoprecipitation indicated that NS depletion leads to dissociation of the components of snoRNPs and the telomerase complex. Third, NS depletion reduced both telomerase activity and the cellular level of pseudouridine, an H/ACA snoRNP-mediated modification of rRNA and other RNAs that are important for their folding and stability. These morphological, biochemical and functional studies demonstrate thatNSplays an important role to maintain nucleolar structure and function on a more fundamental level than previously thought.
AB - Nucleostemin (NS) is a nucleolar protein involved in the regulation of cell proliferation. Both overexpression and knock-down ofNSincrease the activity of the tumor suppressor protein p53, resulting in cell cycle arrest. In addition, NS regulates processing of pre-rRNA and consequently the level of total protein synthesis. Here, we describe a previously uncharacterized function of NS in the maintenance of the tripartite nucleolar structure as well as the integrity of small nucleolar ribonucleoproteins (snoRNPs). NS is also necessary to maintain the telomerase complex which shares common protein subunits with the H/ ACA box snoRNPs. First, immunofluorescence microscopy and electron microscopy demonstrated that knockdown of NS disorganized the nucleolar architecture, in particular, the dense fibrillar component where snoRNPs are localized. Second, gel filtration chromatography and immunoprecipitation indicated that NS depletion leads to dissociation of the components of snoRNPs and the telomerase complex. Third, NS depletion reduced both telomerase activity and the cellular level of pseudouridine, an H/ACA snoRNP-mediated modification of rRNA and other RNAs that are important for their folding and stability. These morphological, biochemical and functional studies demonstrate thatNSplays an important role to maintain nucleolar structure and function on a more fundamental level than previously thought.
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U2 - 10.1074/jbc.M109.013342
DO - 10.1074/jbc.M109.013342
M3 - Article
C2 - 19648109
AN - SCOPUS:70350400854
SN - 0021-9258
VL - 284
SP - 26685
EP - 26694
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 39
ER -