Maintenance of cells in a quiescent state after terminal differentiation occurs through a number of mechanisms that regulate the activity of the E2F family of transcription factors. We report here that changes in the subcellular compartmentalization of the E2F family proteins are required to prevent nuclei in terminally differentiated skeletal muscle from reentering S phase. In terminally differentiated L6 myotubes, E2F-1, E2F-3, and E2F-5 were primarily cytoplasmic, E2F-2 was nuclear, whereas E2F-4 became partitioned between both compartments. In these same cells, pRB family members, pRB, p107, and p130 were also nuclear. This compartmentalization of the E2F-1 and E2F-4 in differentiated muscle cells grown in vitro reflected their observed subcellular location in situ. We determined further that exogenous E2F-1 or E2F-4 expressed in myotubes at levels fourfold greater than endogenous proteins compartmentalized identically to their endogenous counterparts. Only when overexpressed at higher levels was inappropriate subcellular location for these proteins observed. At these levels, induction of the E2F-regulated genes, cyclins A and E, and suppression of factors associated with myogenesis, myogenin, and p21Cip1was observed. Only at these levels of E2F expression did nuclei in these terminally differentiated cells enter S phase. These data demonstrate that regulation of the subcellular compartmentalization of E2F-family members is required to maintain nuclei in a quiescent state in terminally differentiated cells.
Skip Nav Destination
Article navigation
20 March 2000
Article|
March 20 2000
Subcellular Compartmentalization of E2f Family Members Is Required for Maintenance of the Postmitotic State in Terminally Differentiated Muscle
R. Montgomery Gill,
R. Montgomery Gill
aDepartment of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
Search for other works by this author on:
Paul A. Hamel
Paul A. Hamel
aDepartment of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
Search for other works by this author on:
R. Montgomery Gill
aDepartment of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
Paul A. Hamel
aDepartment of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
Abbreviations used in this paper: BrdU, bromodeoxyuridine; DAPI, 4,6-diamidino-2-phenylindole; EMSA, electrophoretic mobility shift assay; GFP, green fluorescent protein; HA, hemagglutinin; LgT, large T antigen; NES, nuclear export signal(s); NLS, nuclear localization signal; SV40, simian virus 40.
Received:
September 09 1999
Revision Requested:
January 20 2000
Accepted:
February 08 2000
Online ISSN: 1540-8140
Print ISSN: 0021-9525
© 2000 The Rockefeller University Press
2000
The Rockefeller University Press
J Cell Biol (2000) 148 (6): 1187–1202.
Article history
Received:
September 09 1999
Revision Requested:
January 20 2000
Accepted:
February 08 2000
Citation
R. Montgomery Gill, Paul A. Hamel; Subcellular Compartmentalization of E2f Family Members Is Required for Maintenance of the Postmitotic State in Terminally Differentiated Muscle. J Cell Biol 20 March 2000; 148 (6): 1187–1202. doi: https://doi.org/10.1083/jcb.148.6.1187
Download citation file:
Sign in
Don't already have an account? Register
Client Account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Sign in via your Institution
Sign in via your InstitutionSuggested Content
Email alerts
Advertisement
Advertisement