Functional aspects of the nuclear matrix.
A model is proposed of the way in which the unwinding of the chromosomal DNA loops is controlled during DNA replication. It is based on the observation of a permanent binding of replication origins to the nuclear matrix and of a transient attachment of replicating DNA regions to sites in the immediate neighbourhood. DNA unwinding is controlled while the replicating loops are reeled through the replication binding sites. Also a mechanism is proposed to explain how the once-per-cycle replication of individual replicons can be controlled. DNA synthesis is initiated at single-stranded loops exposed by tandemly repeated DNA sequences at the replication origins. The single-stranded loops turn into fully double-stranded DNA during replication, becoming inaccessible for a second initiation during the same cell cycle. The configuration competent for initiation is restored by specific protein-DNA rearrangements coupled to mitotic condensation of the matrix into chromosomal scaffolds and its reversal.
Wanka
F
F
Department of Cell Biology, University of Nijmegen, The Netherlands.
D001483:Base Sequence; D004261:DNA Replication; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015530:Nuclear Matrix / Q000502:physiology*; D009690:Nucleic Acid Conformation; D012091:Repetitive Sequences, Nucleic Acid