Changes in chromatin structure at the replication fork. II The DNPs containing nascent DNA and a transient chromatin modification detected by DNAase I.
AUTOR(ES)
Galili, G
RESUMO
Discrete deoxyribonucleoproteins (DNPs) containing nascent and/or bulk DNA, were obtained by fractionating micrococcal nuclease digests of nuclei form 3H-thymidine pulse (15-20 sec) and 14C-thymidine long (16 h) labeled sea urchin embryos in polyacrylamide gels. One of these DNPs was shown to contain the micrococcal nuclease resistant 300 bp "large nascent DNA" described in Cell 14, 259-267, 1978. The bulk and nascent mononucleosome fractions provided evidence for the preferential digestion by micrococcal nuclease of nascent over bulk linker regions to yield mononucleosome cores with nascent DNA. DNAase I was used to probe whether any nascent DNA is in nucleosomes. Nascent as well as bulk single-stranded DNA fragments occurred in multiples of 10.4 bases with higher than random frequencies of certain fragment sizes (for instance 83 bases) as expected from a nucleosome structure. However, a striking background of nascent DNA between nascent DNA peaks was observed. This was eliminated by a pulse-chase treatment or by digestion of pulse-labeled nuclei with micrococcal nuclease together with DNAase I. One of several possible interpretations of these results suggests that a transient change in nucleosome structure may have created additional sites for the nicking of nascent DNA by DNAase I; the micrococcal nuclease sensitivity of the interpeak radioactivity suggest its origin from the linker region. Endogenous nuclease of sea urchin embryos cleaves chromatin DNA in a manner similar to that of DNAase I.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=327410Documentos Relacionados
- Disruption of the nucleosomes at the replication fork.
- Processing of telomeric DNA ends requires the passage of a replication fork.
- Flexibility in RNA priming of Okazaki pieces at the E. coli replication fork.
- Mammalian DNA polymerase alpha holoenzymes with possible functions at the leading and lagging strand of the replication fork.
- Local chromatin structure at the ribosomal DNA causes replication fork pausing and genome instability in the absence of the S. cerevisiae DNA helicase Rrm3p