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EMBO reports 4, 10, 959–963 (2003)
doi:10.1038/sj.embor.embor938
AOP Published online: 12 September 2003
Blm3 is part of nascent proteasomes and is involved in a late stage of nuclear proteasome assembly
Marion Fehlker1, 2, Petra Wendler1, 2, Andrea Lehmann1, 2 & Cordula Enenkel1
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1 Institut für Biochemie, Humboldt
Universität zu Berlin, Universitätsklinikum Charité,
Monbijoustrasse 2, D-10117 Berlin,
Germany
2 These authors contributed equally to this work
To whom correspondence should be addressed
Cordula Enenkel Tel: +30 450 528158; Fax: +30 450 528916;
cordula.enenkel@charite.de
Received 3 April 2003; Accepted 8 August 2003; Published online 12 September 2003.
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Abstract
Proteasomes are multisubunit proteases that are responsible for
regulated proteolysis. The degradation of the proteasomal maturation factor,
named Ump1 in yeast, completes the autocatalytic processing of inactive
precursor complexes into the proteolytically active core particle (CP) of the
proteasome. We have identified Blm3, a conserved nuclear protein, as a new
component of Ump1-associated precursor complexes. A lack of Blm3 resulted in an
increased rate of precursor processing and an accelerated turnover of Ump1,
which suggests that Blm3 prevents premature activation of proteasomal CPs. On
the basis of biochemical fractionation experiments combined with in vivo
localization studies, we propose that Blm3 joins nascent CPs inside the nucleus
to coordinate late stages of proteasome assembly in yeast.
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