[Coordinator's Note: This message doesn't precisely meet the criteria of cytometry as
cell MEASUREMENT, but I've worked with Dr. Cooper at Michigan, and think there may
possibly be some interest and expertise in the mammalian cell cycle and its regulation
in our community, and think the message is worth posting. You may want to reply directly
to Dr. Cooper if your response might stray too far from our main focus.
Thanks,
Steve Kelley ]
Dear Friends of the Cell Cycle,
Over the past few years there has been a lot of discussion and
writing regarding the relationship of the G1-phase to the control of the
cell cycle. A lot of this discussion centered on reevaluations of
analytical work that was reinterpreted as showing that there was an
alternative explanation for much of the data supporting the exitence of
G1-phase events, arrest points, decision points, and so forth.
Although most of my scientific career has been involved with
bacteria, over the last year or so I have begun working on eukaryotic
cells with a view to presenting experimental work supporting these ideas.
I now write to let the members of the group know of a paper that is
published in IUBMB-Life (International Union of Biochemistry and Molecular
Biology-LIFE), Volume 28, Pages 225-230 (1999) which presents experimental
data related to the nature of the G1 phase. The paper is entitled
"Phosphorylation-Dephosphorylation of Retinoblastoma Protein is not
Necessary for Passage through the Mammalian Cell Cycle" (by Cooper, Yu, and
Shayman). Briefly summarized, this paper shows that one can grow cells
without having a G1-phase phosphorylation event (and the presumed mitotic
dephosphorylation event), but most important, this paper explains why
others have interpreted their results to support a G1-phase phosphorylation
event.
A second paper of interest which applies to the same problem is
coming out soon in Progress in Cell Cycle Research (volume 4, pages 27-39
(1999)) and which is entitled "The Continuum Model and G1-control of the
mammalian cell cycle". This is a review article which summarizes the
alternative view of the eukaryotic cell cycle. In particular, it
demonstrates that it is not possible, by starvation or inhibition methods,
to synchronize cells. Ever.
If you are unable to obtain these articles in your library, and are
interested in the subject, please let me know and I will send you reprints
of the articles.
In addition to these two published papers, there is a manuscript
submitted for publication entitled "Revisiting Retinoblastoma
Phosphorylation During the Mammalian Cell Cycle" (by Cooper and Shayman)
which is a thorough reanalysis of the data supporting G1-phase Rb
phosphorylation. If you are interested in this subject, let me know and I
will send you a preprint.
I write this public letter in the hope of reaching four types of
researchers:
First, I want to reach those who are thoroughly committed to the
current viewpoint so that they may get back to me with critiques and
comments on these articles. Only by putting my ideas against strong and
sharp critiques can I sharpen the arguments and clarify the ideas.
Second, I want to reach those who have been reading so much about
G1-phase events (restriction points, G(0), synchronization by arrest in G1,
etc.) but who are not close to the subject because they may not know of the
other viewpoint. Because there is so much material out there it is hard to
get hold of the alternative viewpoint and thus the current viewpoint
dominates by default.
Third, I want to reach people who have data that may fit with the
alternative model, or who have data that they have not been able to
interpret within the current viewpoint. For example, perhaps you have
tried to synchronize cells by some particular G1-phase arrest protocol and
could not do it. You may have thought that either your cells or your
conditions are just not right, but this alternative viewpoint can now give
you support for your own experiments.
Fourth, I would like to meet people who share my view and who are
interested in sharing ideas regarding an alternative view of the mammalian
cell cycle.
Again, I look forward to hearing from anyone who has an interest in
the control of the mammalian cell cycle.
Sincerely, Stephen Cooper (cooper@umich.edu)
Dr. Stephen Cooper
Department of Microbiology and Immunology
University of Michigan Medical School
Ann Arbor MI 48109-0620
e-mail: cooper@umich.edu
phone: 734-764-4215
FAX: 734-764-3562
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