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c‐Myc localization within the nucleus: Evidence for association with the PML nuclear body
Author(s) -
Smith Kelly P.,
Byron Meg,
O'Connell Brenda C.,
Tam Rose,
Schorl Christoph,
Guney Isil,
Hall Lisa L.,
Agrawal Pooja,
Sedivy John M.,
Lawrence Jeanne B.
Publication year - 2004
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.20273
Subject(s) - nucleolus , proteasome , endogeny , nucleus , biology , microbiology and biotechnology , ubiquitin , null cell , nuclear protein , transfection , cell nucleus , nuclear localization sequence , cancer research , cell culture , transcription factor , gene , biochemistry , genetics
Definitive localization of c‐Myc within the nucleus is important to fully understand the regulation and function of this oncoprotein. Studies of c‐Myc distribution, however, have produced conflicting results. To overcome technical challenges inherent in c‐Myc cytology, we use here three methods to visualize c‐Myc and in addition examine the impact of proteasome inhibition. EYFP or HA‐tagged Myc was reintroduced by stable transfection into myc null diploid rat fibroblasts, replacing endogenous Myc with tagged Myc expressed at or near normal levels. This tagged Myc is shown to functionally replace the endogenous Myc by restoration of normal cell morphology and growth rate. We were able to confirm key findings using antibodies to the endogenous c‐Myc and/or its partner, Max. Contrary to some published reports, by all three methods the c‐Myc protein in rat fibroblasts distributes predominantly throughout the nucleus in a dispersed granular pattern, avoiding the nucleolus. Importantly, however, several findings provide evidence for an unanticipated relationship between c‐Myc and PML nuclear bodies, which is enhanced under conditions of proteasome inhibition. Evidence of Max concentration within PML bodies is shown both with and without proteasome inhibition, strengthening the relationship between PML bodies and Myc/Max. Some accumulation of Myc and Max in nucleoli upon proteasome inhibition is also observed, although co‐localization of ubiquitin was only seen with PML bodies. This work provides a comprehensive study of c‐Myc distribution and also presents the first evidence of a relationship between turnover of this oncoprotein and PML nuclear bodies, known to break down in certain cancers. © 2004 Wiley‐Liss, Inc.