Cell fusion-induced quick change in replication time of the inactive mouse X chromosome: an implication for the maintenance mechanism of late replication.
It is unknown how and why the genetically inactivated mammalian X chromosome replicates late in S phase. There are also occasional inactive X chromosomes characterized by an opposite behavior replicating early in S phase. Two clonal cell lines, MTLB3 and MTLH8, isolated from a cultured murine T-cell lymphoma have an allocyclic X chromosome of the latter type. This precociously replicating X chromosome was judged to be genetically inactive as the late replicating one. Immediately after fusion with another cell line, the precociously replicating X chromosome from these cells starts to replicate late in S phase. This finding seems to suggest that late replication characterizing the inactive X chromosome is actively maintained by a trans-acting factor in female somatic cells, and that its lack entails a switch from late replication to precocious replication. It remains unknown whether this presumptive factor also modifies the autosomal replication pattern.
Yoshida
I
I
Research Center for Molecular Genetics, Faculty of Science, Hokkaido University, Sapporo, Japan.
Kashio
N
N
Takagi
N
N
D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle / Q000235:genetics*; D004261:DNA Replication; D004303:Dosage Compensation, Genetic; D005260:Female; D005786:Gene Expression Regulation; D006822:Hybrid Cells; D007621:Karyotyping; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D016196:S Phase / Q000235:genetics; D014407:Tumor Cells, Cultured