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  • 1
    ISSN: 1617-4623
    Keywords: Schizosaccharomyces pombe ; DNA-damage inducibility ; Damage-responsive element ; Upstream activating sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract TheSchizosaccharomyces pombe rhp51 + gene encodes a recombinational repair protein that shares significant sequence identities with the bacterial RecA and theSaccharomyces cerevisiae RAD51 protein. Levels ofrhp51 + mRNA increase following several types of DNA damage or inhibition of DNA synthesis. Anrhp51::ura4 fusion gene was used to identify the cis-acting promoter elements involved in regulatingrhp51 + expression in response to DNA damage. Two elements, designated DRE1 and DRE2 (fordamage-responsiveelement), match a decamer consensus URS (upstream repressing sequence) found in the promoters of many other DNA repair and metabolism genes fromS. cerevisiae. However, our results show that DRE1 and DRE2 each function as a UAS (upstream activating sequence) rather than a URS and are also required for DNA-damage inducibility of the gene. A 20-bp fragment located downstream of both DRE1 and DRE2 is responsible for URS function. The DRE1 and DRE2 elements cross-competed for binding to two proteins of 45 and 59 kDa. DNase I footprint analysis suggests that DRE1 and DRE2 bind to the same DNA-binding proteins. These results suggest that the DRE-binding proteins may play an important role in the DNA-damage inducibility ofrhp51 + expression.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Key wordsSchizosaccharomyces pombe ; SNF2/SWI2 protein family ; ATPase/helicase domains ; DNA-binding domain ; Chromodomain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The SNF2/SWI2 ATPase/helicase family comprises proteins from a variety of species, which serve a number of functions, such as transcriptional regulation, maintenance of chromosome stability during mitosis, and various types of DNA repair. Several proteins with unknown functions are also included in this family. The number of genes that belong to this family is rapidly expanding, which makes it easier to analyze the common biological functions of the family members. This study was designed to clone the SNF2/SWI2 helicase-related genes from the fission yeast Schizosaccharomyces pombe in the hope that this would help to elucidate the common functions of the proteins in this family. The hrp1 + (helicase-related gene from S. p ombe) gene was initially cloned by PCR amplification using degenerate primers based on conserved SNF2 motifs within the ERCC6 gene, which encodes a protein involved in DNA excision repair. The hrp1 + ORF codes for an 1373-amino acid polypeptide with a molecular mass of 159 kDa. Like other SNF2/SWI2 family proteins, the deduced amino acid sequence of Hrp1 contains DNA-dependent ATPase/7 helicase domains, as well as a chromodomain and a DNA-binding domain. This configuration is similar to that of mCHD1 (mouse chromo-ATPase/helicase-DNA-binding protein 1), suggesting that Hrp1 is a S. pombe homolog of mCHD1, which is thought to function in altering the chromatin structure to facilitate gene expression. Northern blot analysis showed that the hrp1 + gene produces a 4.6-kb transcript, which reaches its maximal level just before the cells enter the exponential growth phase, and then decreases gradually. DNA-damaging agents, such as MMS, MNNG and UV, decrease the rate of transcription of hrp1 +. Deletion of the hrp1 + gene resulted in accelerated cell growth. On the other hand, overexpression of Hrp1 caused a reduction in growth rate. These results indicate that hrp1 + may act as a negative regulator of cellular growth.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1617-4623
    Keywords: Key words Rat ; DNA topoisomerase IIα ; Saccharomyces cerevisiae ; top2ts ; Complementation ; Leucine zipper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A series of yeast expression plasmids which comprise segments of the cDNA sequences encoding rat topo IIα have been constructed. The transcription of these constructs is under the control of the yeast GAL1 promoter. Galactose-dependent expression of the cloned rat topo IIα cDNA complemented a yeast top2 ts mutation, as well as a deletion mutation at the yeast TOP2 locus. Truncation of 12 N-terminal amino acids and/or 158 C-terminal amino acids of rat topo IIα had no effect on its ability functionally to substitute for top2 ts . Moreover, a cDNA construct with mutated putative leucine zipper domain (amino acids 993–1013) retained the complementation activity. These observations suggest that transformants capable of conditional topo IIα expression can be exploited as a useful model system for studies on the structure-function relationships of wild-type and mutated topo IIα, as well as the interplay of potential antitumor drugs with the enzyme.
    Type of Medium: Electronic Resource
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