Isolation and characterization of a human cDNA clone encoding a novel DNA topoisomerase II homologue from HeLa cells

Austin, Caroline A.; Fisher, L. Mark

doi:10.1016/0014-5793(90)81520-x

Cited by 54 publications

(31 citation statements)

References 10 publications

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“…Total cellular RNA was isolated from synchronized cells in G 1 (2,6, or 10 h postcollection), S (10 or 16 h), and G 2 ϩM (16, 18, or 20 h) and then analyzed by Northern blotting as in Fig. 1, using a human topoisomerase II␤ cDNA probe ( Fig.…”

Section: Resultsmentioning

confidence: 99%

The Cell Cycle-Coupled Expression of Topoisomerase IIα during S Phase Is Regulated by mRNA Stability and Is Disrupted by Heat Shock or Ionizing Radiation

Goswami

Roti

Hunt

1996

Molecular and Cellular Biology

109

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Topoisomerase II is a multifunctional protein required during DNA replication, chromosome disjunction at mitosis, and other DNA-related activities by virtue of its ability to alter DNA supercoiling. The enzyme is encoded by two similar but nonidentical genes: the topoisomerase II␣ and II␤ genes. In HeLa cells synchronized by mitotic shake-off, topoisomerase II␣ mRNA levels were found to vary as a function of cell cycle position, being 15-fold higher in late S phase (14 to 18 h postmitosis) than during G 1 phase. Also detected was a corresponding increase in topoisomerase II␣ protein synthesis at 14 to 18 h postmitosis which resulted in significantly higher accumulation of the protein during S and G 2 phases. Topoisomerase II␣ expression was not dependent on DNA synthesis during S phase, which could be inhibited without effect on the timing or level of mRNA expression. Mechanistically, topoisomerase II␣ expression appears to be coupled to cell cycle position mainly through associated changes in mRNA stability. When cells are in S phase and mRNA levels are maximal, a half-life of greater than 4 h was observed. However, during G 1 phase, when cellular levels are lowest, the half-life of topoisomerase II␣ mRNA was determined to be approximately 30 min. A similar decrease in mRNA stability was also induced by two external factors known to delay cell cycle progression. Treatment of S-phase cells, at the time of maximum topoisomerase II␣ mRNA stability, with either ionizing radiation (5 Gy) or heat shock (45؇C for 15 min) caused the accumulated topoisomerase II␣ mRNA to decay. This finding suggests a potential relationship between stress-induced decreases in topoisomerase II␣ expression and cell cycle progression delays in late S/G 2 .The double-stranded nature of the DNA molecule presents special problems during chromosomal replication and segregation. Movement of the replication fork along the DNA molecule generates positive supercoiling in advance while the replicated parental strands in its wake are negatively supercoiled. Topological problems also arise near the end of replication when adjacent replication forks converge. Depending on the relative unwinding rate of the parental or progeny strands, either an intertwined or a gapped structure is formed (47). Unless untangled, the former structure leads to chromosome breakage, nondisjunction, and cell death (20). DNA topology in the cell is controlled through the action of two types of topoisomerase enzymes (see references 20 and 46 for reviews). Type I topoisomerases introduce into the duplex DNA molecule transient single-strand nicks which act as swivels during DNA replication or relieve the torsional stress associated with RNA transcription. Topoisomerase II enzymes relax, catenate, or decatenate DNA by introducing transient double-strand breaks which allow another DNA segment to pass through. While topoisomerase II is also capable, in theory, of relaxing transcription and replication induced supercoiling, it appears that topoisomerase I is mainly responsible for ...

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Section: Resultsmentioning

confidence: 99%

The Cell Cycle-Coupled Expression of Topoisomerase IIα during S Phase Is Regulated by mRNA Stability and Is Disrupted by Heat Shock or Ionizing Radiation

Goswami

Roti

Hunt

1996

Molecular and Cellular Biology

109

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“…Mammals possess two topoisomerase II isoforms, α and β, encoded by the TOP2A and TOP2B genes respectively. 22,23 Although the isoforms have very similar enzymatic characteristics in vitro and share 70% amino acid identity, topoisomerase IIα and -β have different though possibly overlapping roles in mammalian cells. Topoisomerase be specifically nucleolar.…”

Section: Histone Deacetylase Inhibition Redistributes Topoisomerase Imentioning

confidence: 99%

Histone deacetylase inhibition redistributes topoisomerase IIb from heterochromatin to euchromatin

Cowell¹,

Papageorgiou²,

Padget³

et al. 2011

nucleus

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“…24,25 Type IIA topoisomerases share significant amino acid sequence homology between species, with the human type II topoisomerases being ~ 40% identical with Saccharomyces cerevisiae topoisomerase II (Top2) (Fig. S1).…”

Section: Introductionmentioning

confidence: 99%

The Structure of DNA-Bound Human Topoisomerase II Alpha: Conformational Mechanisms for Coordinating Inter-Subunit Interactions with DNA Cleavage

Wendorff

Schmidt

Heslop

et al. 2012

Journal of Molecular Biology

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196

188

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Type II topoisomerases are required for the management of DNA superhelicity and chromosome segregation, and serve as frontline targets for a variety of small-molecule therapeutics. To better understand how these enzymes act in both contexts, we determined the 2.9-Å-resolution structure of the DNA cleavage core of human topoisomerase IIα (TOP2A) bound to a doubly nicked, 30-bp duplex oligonucleotide. In accord with prior biochemical and structural studies, TOP2A significantly bends its DNA substrate using a bipartite, nucleolytic center formed at an N-terminal dimerization interface of the cleavage core. However, the protein also adopts a global conformation in which the second of its two inter-protomer contact points, one at the C-terminus, has separated. This finding, together with comparative structural analyses, reveals that the principal site of DNA engagement undergoes highly quantized conformational transitions between distinct binding, cleavage, and drug-inhibited states that correlate with the control of subunit–subunit interactions. Additional consideration of our TOP2A model in light of an etoposide-inhibited complex of human topoisomerase IIβ (TOP2B) suggests possible modification points for developing paralog-specific inhibitors to overcome the tendency of topoisomerase II-targeting chemotherapeutics to generate secondary malignancies.

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Isolation and characterization of a human cDNA clone encoding a novel DNA topoisomerase II homologue from HeLa cells

Cited by 54 publications

References 10 publications

The Cell Cycle-Coupled Expression of Topoisomerase IIα during S Phase Is Regulated by mRNA Stability and Is Disrupted by Heat Shock or Ionizing Radiation

The Cell Cycle-Coupled Expression of Topoisomerase IIα during S Phase Is Regulated by mRNA Stability and Is Disrupted by Heat Shock or Ionizing Radiation

Histone deacetylase inhibition redistributes topoisomerase IIb from heterochromatin to euchromatin

The Structure of DNA-Bound Human Topoisomerase II Alpha: Conformational Mechanisms for Coordinating Inter-Subunit Interactions with DNA Cleavage

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