Interphase cell cycle dynamics of a late-replicating, heterochromatic homogeneously staining region: Precise choreography of condensation/decondensation and nuclear positioning

Gang Li, Gail Sudlow, Andrew S. Belmont

Research output: Contribution to journalArticlepeer-review

Abstract

Recently we described a new method for in situ localization of specific DNA sequences, based on lac operator/repressor recognition (Robinett, C.C., A. Straight, G. Li, C. Willhelm, G. Sudlow, A. Murray, and A.S. Belmont. 1996. J. Cell Biol. 135:1685-1700). We have applied this methodology to visualize the cell cycle dynamics of an ~90 Mbp, late-replicating, heterochromatic homogeneously staining region (HSR) in CHO cells, combining immunostaining with direct in vivo observations. Between anaphase and early G1, the HSR extends approximately twofold to a linear, ~0.3-μm-diam chromatid, and then recondenses to a compact mass adjacent to the nuclear envelope. No further changes in HSR conformation or position are seen through mid-S phase. However, HSR DNA replication is preceded by a decondensation and movement of the HSR into the nuclear interior 4-6 h into S phase. During DNA replication the HSR resolves into linear chromatids and then recondenses into a compact mass; this is followed by a third extension of the HSR during G2/prophase. Surprisingly, compaction of the HSR is extremely high at all stages of interphase. Preliminary ultrastructural analysis of the HSR suggests at least three levels of large-scale chromatin organization above the 30-nm fiber.

Original languageEnglish (US)
Pages (from-to)975-989
Number of pages15
JournalJournal of Cell Biology
Volume140
Issue number5
DOIs
StatePublished - Mar 9 1998

ASJC Scopus subject areas

  • Cell Biology

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