Dataset Information

Human TOP3: a single-copy gene encoding DNA topoisomerase III.

ABSTRACT: A human cDNA encoding a protein homologous to the Escherichia coli DNA topoisomerase I subfamily of enzymes has been identified through cloning and sequencing. Expressing the cloned human cDNA in yeast (delta)top1 cells lacking endogenous DNA topoisomerase I yielded an activity in cell extracts that specifically reduces the number of supercoils in a highly negatively supercoiled DNA. On the basis of these results, the human gene containing the cDNA sequence has been denoted TOP3, and the protein it encodes has been denoted DNA topoisomerase III. Screening of a panel of human-rodent somatic hybrids and fluorescence in situ hybridization of cloned TOP3 genomic DNA to metaphase chromosomes indicate that human TOP3 is a single-copy gene located at chromosome 17p11.2-12.

SUBMITTER: Hanai R

PROVIDER: S-EPMC39666 | biostudies-other | 1996 Apr

REPOSITORIES: biostudies-other

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Human TOP3: a single-copy gene encoding DNA topoisomerase III.

Hanai R R Caron P R PR Wang J C JC

Proceedings of the National Academy of Sciences of the United States of America 19960401 8

A human cDNA encoding a protein homologous to the Escherichia coli DNA topoisomerase I subfamily of enzymes has been identified through cloning and sequencing. Expressing the cloned human cDNA in yeast (delta)top1 cells lacking endogenous DNA topoisomerase I yielded an activity in cell extracts that specifically reduces the number of supercoils in a highly negatively supercoiled DNA. On the basis of these results, the human gene containing the cDNA sequence has been denoted TOP3, and the protein ...[more]

PMID: 8622991

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Project description:PurposeA Topoisomerase 1 (Top1) poison is frequently included in the treatment regimens for metastatic colorectal cancer (mCRC). However, no predictive biomarkers for Top1 poisons are available. We here report a study on the TOP1 gene copy number in CRC patients and its association with patient prognosis and tumor cell proliferation.Experimental designThe study included TOP1 and CEN-20 fluorescence in situ hybridization (FISH) analyses on formalin fixed paraffin embedded (FFPE) tissue sections from 154 stage III CRC chemonaïve patients. The frequencies of aberration in the TOP1 gene copy number, the CEN-20 copy number and the TOP1/CEN-20 ratio were analyzed and associated with overall survival (OS), time to recurrence (TTR) and in a subgroup analysis of rectal cancer patients only with time to local recurrence (LR in RC). Moreover, the TOP1 and CEN-20 copy numbers were correlated with the tumor Ki67 proliferation index.Results35.7% of the tumors had an increased TOP1 copy number above 4n gene copies per cell and 28.6% and 9.7% had a TOP1/CEN-20 ratio ?1.5 or ?2.0, respectively. The TOP1 copy number and the TOP1/CEN-20 ratios were separately added into multivariate analyses as continuous variables, in which also age, gender, primary tumor location and Ki67 status were added as covariates. In contrast to the TOP1/CEN-20 ratio, the TOP1 copy number was significantly associated with OS (HR: 0.62; 95% CI: 0.42-0.90; p = 0.01). Neither the TOP1 copy number nor the ratio was significantly associated with TTR and only the TOP1/CEN-20 ratio was significantly associated with LR in RC (HR: 0.25; 95% CI: 0.08-0.83; p = 0.02). No significant correlation was found between the TOP1 copy number and proliferation, while a weak and inverse correlation between the CEN-20 copy number and proliferation was observed.ConclusionsThis study showed that increased TOP1 gene copy numbers are frequent findings in cancer cells in stage III CRC tumors but unrelated to the proliferative status of the tumors. The association with prognosis is important to consider when planning and analyzing future studies investigating TOP1 as a potential predictive biomarker for Top1 poisons.

Dataset Information

Human TOP3: a single-copy gene encoding DNA topoisomerase III.

Publications

Human TOP3: a single-copy gene encoding DNA topoisomerase III.

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