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E2F5 and LEK1 Translocation to the nucleus is an early event demarcating myoblast quiescence
Author(s) -
Reed Sarah A.,
Ouellette Sara E.,
Liu Xiaosong,
Allen Ronald E.,
Johnson Sally E.
Publication year - 2007
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.21256
Subject(s) - microbiology and biotechnology , myogenesis , nucleus , cytoplasm , myocyte , mapk/erk pathway , chromosomal translocation , cell cycle , biology , kinase , cell nucleus , nuclear export signal , chemistry , cell , biochemistry , gene
Raf/MEK/ERK signaling in skeletal muscle cells affects several aspects of myogenesis that are correlated with the duration and intensity of the input signal. 23A2RafER DD myoblasts directing elevated levels of Raf kinase for 24 h are mitotically inactive. Removal of the stimulus results in cell cycle re‐entry and proliferation. Using a proteomic approach, E2F5 and LEK1 were detected in the nuclei of Raf‐arrested myoblasts. Disruption of MEK1 activity prevents phosphorylation of ERK1/2 and nuclear translocation of E2F5 and LEK1. The pocket proteins, p107 and p130, remain in the cytoplasm of growth arrested myoblasts irrespective of Raf/ERK activation while pRb translocates to the nucleus. Importantly, both E2F5 and LEK1 are found in the nuclei of non‐dividing satellite cells and myonuclei in vivo and in vitro. Our results indicate that Raf‐arrested myoblasts may serve as a model system for satellite cell cycle studies and that E2F5 and LEK1 translocation to the nucleus is an important first step during entry into quiescence. J. Cell. Biochem. 101: 1394–1408, 2007. © 2007 Wiley‐Liss, Inc.