topoisomerase I, Topo I, l(1)G0229, l(1)G0278, l(1)G0134
Gene model reviewed during 5.50
Low-frequency RNA-Seq exon junction(s) not annotated.
Annotated transcripts do not represent all possible combinations of alternative exons and/or alternative promoters.
Gene model reviewed during 5.39
Gene model reviewed during 5.55
Homology to other Top1 proteins is concentrated in two regions. The Drosophila enzyme is larger than the enzymes from yeast and human and is uniquely characterized by a Ser/His rich hydrophilic domain of 200aa at its amino terminus. The bacterially expressed protein was shown to have classic eukaryotic DNA topoisomerase I activity, distinguished by the fact that it can relax both positively and negatively supercoiled DNA in the absence of a divalent cation.
Camptothecin-induced Top1 protein cleavage sites were mapped in the Act5C, Act57A, and hsp70 genes. Top1 protein cleavage sites were localized to the transcribed portions of the Hsp70B and Act5C genes, and only when they are transcriptionally active. None were found in a transcriptionally inactive Act57A gene.
Interacts with Topors.
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\Top1 using the Feature Mapper tool.
GBrowse - Visual display of RNA-Seq signalsView Dmel\Top1 in GBrowse 2
Please Note This section lists cDNAs and ESTs that fall within the genomic extent of the gene model, which may include cDNAs and ESTs of genes within introns, or of overlapping genes. Please see GBrowse for alignment of the cDNAs and ESTs to the gene model.
For each fully sequenced cDNA the DGRC maintains various forms of the cDNA (e.g tagged or untagged) in several different host vectors for subsequent cloning and expression in Drosophila and Drosophila cell lines.
DNA-protein interactions: genome-wide binding profile assayed for Top1 protein in Kc167 cells; see Chromatin_types_NKI collection report. Individual protein-binding experiments listed under "Samples" at GEO_GSE22069 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE22069).
Top1 plays an essential role in many developmental stages active in cell proliferation.
The genomic organisation of the Top1 locus has been determined and its expression pattern has been analysed.
The N-terminal 430 amino acid residues of Top1 are inconsequential for its catalytic activity. The N-terminal region directs Top1-Ecol\lacZ fusion constructs to transcriptionally active loci in the polytene chromosomes.
Using P element mutagenesis a mutant deficient in topoisomerase 1 was generated: topoisomerase 1 is essential for growth and development.
DNA topoisomerase 1 was cloned by homology to consensus eukaryotic DNA topoisomerase 1 sequence, and expressed in an E.coli expression system.
The interaction of Top1 and Top2 gene products with transcriptionally active and inactive Act5C, Act57B and Hsp70B has been compared. Topoisomerase I binding sites are found in the transcribed portions of the Hsp70B and Act5C genes, and only when they are transcriptionally active. It does not associate with a transcriptionally inactive Act57B gene.