TY - JOUR
T1 - Evidence for a relationship between DNA methylation and DNA replication from studies of the 5-azacytidine-reactivated allocyclic X chromosome
AU - Schmidt, Malgorzata
AU - Wolf, Stanley F.
AU - Migeon, Barbara R.
N1 - Funding Information:
This work was supportedb y NIH Grant HD 05465.M . S. is a Fellow of the Eppley Foundation.W e are gratefult o Joyce Axelman for her assistancew ith the hybrid cells.
PY - 1985/6
Y1 - 1985/6
N2 - We examined the sequence of DNA synthesis of the human active, inactive and reactivated X chromosomes in mouse-human hybrid cells. The two independent reactivants, induced by 5-azacytidine (5-azaC), expressed human hypoxanthinephosphoribosyl transferase (HPRT), and one also expressed human glucose-6-phosphate dehydrogenase (G6PD) and phosphoglycerate kinase (PGK). Restriction enzyme analysis of DNA methylation at the re-expressed loci revealed hypomethylation of CpG clusters, that characterizes the relevant genes on the active X. The transfer of active and inactive X chromosomes from the native environment of the human fibroblast to the foreign environment of the hybrid cell did not affect the specific replication sequence of either human X chromosome. The silent X chromosome when reactivated, remained allocyclic, and the first bands to replicate were the same as prior to reactivation. In one reactivant, however, further progression of replication was significantly altered with respect to the order in which bands were synthesized. This alteration in the replication of the silent X following 5-azaC-induced reactivation suggests that DNA methylation may modulate the replication kinetics of Chromosomal DNA.
AB - We examined the sequence of DNA synthesis of the human active, inactive and reactivated X chromosomes in mouse-human hybrid cells. The two independent reactivants, induced by 5-azacytidine (5-azaC), expressed human hypoxanthinephosphoribosyl transferase (HPRT), and one also expressed human glucose-6-phosphate dehydrogenase (G6PD) and phosphoglycerate kinase (PGK). Restriction enzyme analysis of DNA methylation at the re-expressed loci revealed hypomethylation of CpG clusters, that characterizes the relevant genes on the active X. The transfer of active and inactive X chromosomes from the native environment of the human fibroblast to the foreign environment of the hybrid cell did not affect the specific replication sequence of either human X chromosome. The silent X chromosome when reactivated, remained allocyclic, and the first bands to replicate were the same as prior to reactivation. In one reactivant, however, further progression of replication was significantly altered with respect to the order in which bands were synthesized. This alteration in the replication of the silent X following 5-azaC-induced reactivation suggests that DNA methylation may modulate the replication kinetics of Chromosomal DNA.
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U2 - 10.1016/0014-4827(85)90455-0
DO - 10.1016/0014-4827(85)90455-0
M3 - Article
C2 - 2408909
AN - SCOPUS:0021824054
SN - 0014-4827
VL - 158
SP - 301
EP - 310
JO - Experimental cell research
JF - Experimental cell research
IS - 2
ER -