Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

Topoisomerases catalyse the interconversion of topological isomers of DNA and have key roles in nucleic acid metabolism. Human cells express two distinct type II topoisomerase isozymes, designated topoisomerase II alpha (170 kDa form) and topoisomerase II beta (180 kDa form). We have isolated cDNA clones encoding the beta isozyme from a human B-cell library. The proposed coding region for the topoisomerase II beta protein is 4,863 nucleotides long and would encode a polypeptide with a calculated M(r) of 182,705. The predicted topoisomerase II beta protein sequence shows striking similarity (72% identical residues) to that of the human alpha isozyme, and homology to topoisomerase II proteins from Drosophila, yeast and bacteria. Regions of greatest amino acid sequence divergence lie at the extreme N-terminus and over a C-terminal domain comprising approximately 25% of the total protein. We have quantified the level of topoisomerase II beta mRNA in a panel of human tumour cell lines of different origin using an RNase protection assay, and compared the level to that of topoisomerase II alpha mRNA. Topoisomerase II beta mRNA was expressed in haemopoietic, epithelial and fibroblast cell lines, although to different extents, with U937 cells (promonocytic leukaemia) showing a particularly high level. There was no obvious relationship in terms of level of expression between the topoisomerase II alpha and beta genes. We have localised the gene encoding topoisomerase II beta protein to chromosome 3p24 in the human genome.

Original publication

DOI

10.1093/nar/20.21.5587

Type

Journal article

Journal

Nucleic Acids Res

Publication Date

11/11/1992

Volume

20

Pages

5587 - 5592

Keywords

Amino Acid Sequence, Base Sequence, Chromosome Mapping, Chromosomes, Human, Pair 3, Cloning, Molecular, DNA, DNA Topoisomerases, Type II, Humans, In Situ Hybridization, Isoenzymes, Male, Molecular Sequence Data, RNA, Messenger, Sequence Homology, Amino Acid, Tumor Cells, Cultured