QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 28 September 2004
doi: 10.1242/jcs.01414

This Article Figures Only Full Text Full Text (PDF) All Versions of this Article: jcs.01414v1 117/22/5303    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shimizu, N. Articles by Shingaki, K. Search for Related Content PubMed PubMed Citation Articles by Shimizu, N. Articles by Shingaki, K.

Macroscopic folding and replication of the homogeneously staining region in late S phase leads to the appearance of replication bands in mitotic chromosomes

Faculty of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-hiroshima, 739-8521, Japan

^* Author for correspondence (e-mail: shimizu{at}hiroshima-u.ac.jp)

Accepted 19 July 2004

The chromosomal G/R bands are alternating domains differing in their nucleotide sequence biases. The bands are also related to the time of replication: pulse-labeling during S phase makes the replication sites as visible as replication bands that are close to the G/R bands in mitotic chromosomes. We previously showed that a plasmid bearing a mammalian replication origin efficiently generated a chromosomal homogeneously staining region (HSR). Here, we analyze the replication of this artificial HSR and show that it was replicated at the last stage of S phase. The HSR was composed of plasmid repeats only; nonetheless, we found that replication sites pulse-labeled during late S phase appeared as bands in the mitotic HSR and their number was dependent on the length of the HSR. Therefore, replication bands might not arise from sequence information per se. To understand the chronological order of appearance of replication sites, we performed a double pulse-chase experiment using IdU and CldU. Replication of the entire HSR required 100-120 minutes. During this period, the replicated sites appeared as bands at the first and last stages, but in between were apparently scattered along the entire HSR. An analysis of S-phase nuclei revealed that the replication started at the periphery of the globular HSR domain, followed by initiation in the internal domain. The replicated HSR appeared as a ring or a pair of extended spirals in late G2-phase nuclei. To account for these findings, we present a model in which the HSR is folded as a coiled-coil structure that is replicated from the outside to the inside in S phase nuclei.

Key words: Homogeneously staining region, Replication, Chromosome band, Heterochromatin

This article has been cited by other articles:

				K.-i. Utani and N. Shimizu How transcription proceeds in a large artificial heterochromatin in human cells Nucleic Acids Res., November 29, 2008; (2008) gkn970v1. [Abstract] [Full Text] [PDF]