Contrasting patterns of DNA strand breakage and ADP-ribosylation- dependent
DNA ligation during granulocyte and monocyte differentiation
Z Khan and GE Francis
Previous studies have shown that structural changes in DNA, including the
ligation of pre-existing DNA breaks and the opening and closure of new
breaks, occur shortly after exposure of granulomonocytic precursors
(CFU-GM) to granulocyte-macrophage colony stimulating activity (GM- CSA).
Monocytic differentiation of CFU-GM is selectively inhibited by compounds
known to inhibit the nuclear enzyme ADP-ribosyl transferase (ADPRT). Since
this enzyme, which transfers ADP-ribose units to chromatin proteins, is
known to activate DNA ligase, we attempted to determine whether ligation of
one or both types of DNA break is required for monocytic differentiation.
Breaks in DNA were examined using the nucleoid sedimentation technique in
which DNA breaks cause loss of DNA supercoiling in nucleoids and
concomitant changes in their sedimentation through neutral sucrose
gradients. We here report that two distinct patterns of DNA strand breakage
and ligation are associated with differentiation to the granulocyte and
monocyte lineages. Monocytic inducers (phorbolester and vitamin D3)
predominantly produce closure of pre-existing strand breaks, whereas
granulocytic inducers (granulocyte colony stimulating activity, G-CSA;
retinoic acid) cause opening and closure of new breaks. Only ligation of
the pre-existing breaks is highly sensitive to inhibition by 3-
methoxybenzamide (a potent ADPRT inhibitor), and only monocytic
differentiation is impaired by addition of this compound. These findings
suggest that DNA structural changes may be directly involved in
granulocyte-macrophage switching.
Volume 69,
Issue 4,
pp. 1114-1119,
04/01/1987
Copyright © 1987 by The American Society of Hematology
