The promoter region of the human type‐I‐DNA‐topoisomerase gene

Abstract

We examined the promoter of the human type-I-DNA topoisomerase gene (hTOP1) for regions protected against DNase I digestion by nuclear proteins from HeLa or from adenovirus-transformed 293 cells. We identified ten protected DNA sequences within 580 bp of DNA upstream of the transcriptional-start sites and one additional site, which is located between the two clusters of transcriptional-start sites. Several of these protein-binding sites have significant similarities to recognition sequences of known transcription factors including factors Spl, octamer transcription factor, CAMP-responsive-element-binding protein (CREB/ATF), NF-KB and members of the Myc-related family of basichelix-loop-helidleucine-zipper proteins. Other protein-binding sites show less or no similarities to known consensus sequences. We investigated the physiological significance of these protein-binding sites using a set of deletion and nucleotide-exchange mutants. We conclude that the expression of the hTOPl gene is regulated by a complex network of negatively and positively acting transcription factors.Topoisomerases are enzymes present in all nucleated cells. They catalyse the relaxation of torsional tension in DNA and participate in all processes requiring the separation of complementary strands in topologically fixed doublestranded DNA. Their participation in DNA replication (Avemann et al., 1988;Holm et al., 1989;Yang et al., 1987; for reviews see Richter and Knippers, 1989;Zhang et al., 1990), transcription (Brill and Sternglanz, 1988;Liu and Wang, 1987;Ostrander et al., 1990;Stewart et al., 1990) and DNA recombination (Bullock et al., 1985;Rose et al., 1990; Wallis et al., 1989; and for a recent review Wang et a]., 1990) has been demonstrated.Eukaryotic type-I DNA topoisomerases resolve positive and negative superhelical turns by introducing transient single-stranded nicks with the simultaneous covalent binding of the enzyme to one DNA end. The intact strand is then passed through the open strand before the nick is rejoined using the energy stored in the diester bond between a protein tyrosine and the DNA 3' phosphate end.Human type-I DNA topoisomerase (hTOPl), a monomeric enzyme of 91 kDa, is encoded by a single gene, lo-

The Activation of c-Jun NH2-terminal Kinase (JNK) by DNA-damaging Agents Serves to Promote Drug Resistance via Activating Transcription Factor 2 (ATF2)-dependent Enhanced DNA Repair

“…Functional c-Jun/ATF2-regulated genes are well known and include interferon (58), E-selectin (30,59,60), TNF-␣ (8) as well as c-Jun itself (12). In addition, genes with roles in DNA repair which bear functional octomeric sites are known (9,10,61,63). For example, the DNA repair protein DNA polymerase-␤ is known to contain a functional octomeric site whose activation is reversibly dependent upon phosphorylation of an activation factor (62).…”

The Jun Kinase/Stress-activated Protein Kinase Pathway Functions to Regulate DNA Repair and Inhibition of the Pathway Sensitizes Tumor Cells to Cisplatin

“…Several enzymes known to be involved in repair of DNA-cisplatin adducts and implicated in cisplatin resistance (20) contain ATF/CREB sites in their promoters including DNA polymerase ␤ (27, 28), topoisomerase I (30, 31), and proliferating cell nuclear antigen, an accessory protein of DNA polymerase delta (32,33). Moreover, transcription of these genes is known to be activated through the ATF/CREB sites upon stimulation by genotoxic agents (27)(28)(29)(30)(31)(32)(33). Thus, the inhibition of induction of any or all of these activities could account for the inhibitory effects of dnJun on DNA repair and the resultant increase in cisplatin sensitivity.…”

Inhibition of Extracellular Signal-regulated Protein Kinase or c-Jun N-terminal Protein Kinase Cascade, Differentially Activated by Cisplatin, Sensitizes Human Ovarian Cancer Cell Line

“…AP-1 and ATF-2 are important transcription factors regulating numerous genes implicated in cell growth, transformation, differentiation, and DNA repair (30, 66 -68). Several enzymes known to be involved in repair of DNA-cisplatin adducts and implicated in cisplatin resistance (13) contain ATF/cAMP-response element-binding protein sites in their promoters including DNA polymerase ␤ (69, 70), topoisomerase I (71,72), and proliferating cell nuclear antigen, an accessory protein of DNA polymerase ␦ (55, 73). Moreover, transcription of these genes is known to be activated through the ATF/cAMP-response element-binding protein sites upon stimulation by genotoxic agents (55, 69 -73).…”