title: Two differentially spliced forms of topoisomerase IIalpha and beta mRNAs are conserved between birds and humans.
abstract: Screening of chicken cDNA libraries has identified four distinct forms of topoisomerase IIalpha and beta cDNAs. Two of these, designated topo IIalpha-1 and topo IIbeta-1, were previously deposited in the database. The other two, topo IIalpha-2 and topo IIbeta-2, are novel variants that appear to be conserved between chicken and human. Topo IIalpha-2 encodes a protein with an additional 35 amino acids inserted after K321 of the chicken topo IIalpha-1 protein sequence. Topo IIbeta-2 encodes a protein missing 86 amino acids following V27 in the topo IIbeta-1 protein sequence. We have also detected several alternatively spliced forms of human topo IIalpha. One of these, topo IIalpha-3, appears to correspond to chicken topo IIalpha-2. The other two are novel. The existence of these alternatively spliced forms in mature cytoplasmic RNA was confirmed by RT-PCR in several cell lines. Interestingly, these alternatively spliced forms carry sites for post-translational modification, suggesting that they may be subject to differential regulation from the canonical forms. These results suggest that cells express a more complex repertoire of topo II isoforms than previously thought, raising the possibility that different forms of topo II may fulfil specialized functions in chromosome dynamics.
authors: Wellcome Centre for Cell Biology, Institute of Cell and Molecular Biology, University of Edinburgh, Edinburgh EH9 3JR, UK.
authors: A S
authors: AS
authors: Petruti-Mot
authors: W C
authors: WC
authors: Earnshaw
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm; D001483:Base Sequence; D002645:Chickens / Q000235:genetics*; D017124:Conserved Sequence; D004247:DNA / Q000737:chemistry / Q000235:genetics; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004268:DNA-Binding Proteins; D014644:Genetic Variation; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D012333:RNA, Messenger; D004247:DNA; D004250:DNA Topoisomerases, Type II