A New Model for Schizosaccharomyces pombe Telomere Recognition: The Telomeric Single-stranded DNA-Binding Activity of Pot11-389

2006 ◽  
Vol 361 (1) ◽  
pp. 80-93 ◽  
Author(s):  
Johnny E. Croy ◽  
Elaine R. Podell ◽  
Deborah S. Wuttke
2006 ◽  
Vol 188 (12) ◽  
pp. 4577-4580 ◽  
Author(s):  
Rajesh Kasiviswanathan ◽  
Jae-Ho Shin ◽  
Zvi Kelman

ABSTRACT The Cdc6 proteins from the archaeon Methanothermobacter thermautotrophicus were previously shown to bind double-stranded DNA. It is shown here that the proteins also bind single-stranded DNA. Using minichromosome maintenance (MCM) helicase mutant proteins unable to bind DNA, it was found that the interaction of MCM with Cdc6 inhibits the DNA binding activity of Cdc6.


1993 ◽  
Vol 13 (12) ◽  
pp. 7303-7310
Author(s):  
S Altiok ◽  
B Groner

Transcription of the beta-casein gene in mammary epithelial cells is regulated by the lactogenic hormones insulin, glucocorticoids, and prolactin. The DNA sequence elements in the promoter which confer the action of the hormones on the transcriptional machinery and the nuclear proteins binding to this region have been investigated. We found that 221 nucleotides of promoter sequence 5' of the RNA start site are sufficient to mediate the induction of a chloramphenicol acetyltransferase reporter gene in transfected HC11 mammary epithelial cells. Deletion of 5' sequences to position -183 results in a construct with enhanced basal activity which still retains inducibility. A -170 beta-casein promoter-chloramphenicol acetyltransferase construct has very low transcriptional activity, which indicates the presence of a negative regulatory in the region between -221 and -183 and a positive regulatory element between -183 and -170. Band shift analysis showed that the promoter region between -194 and -163 specifically binds two nuclear proteins. The proteins are sequence-specific, single-stranded DNA-binding proteins which exclusively recognize the upper DNA strand and most likely play a repressing role in transcription. DNA binding activity of these nuclear proteins was observed only in nuclear extracts from mammary glands of mice in late pregnancy and postlactation, not during lactation. Hormonal control of the DNA binding activity of these proteins was also observed in the mammary epithelial cell line HC11. Mixing experiments showed that extracts from mammary tissue of lactating mice and from lactogenic hormone-treated HC11 cells contain an activity which can suppress the DNA binding of the single-stranded DNA-binding proteins.2+ identical specificity to the single-stranded DNA.


Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2437-2437
Author(s):  
Ying Cai ◽  
Lalitha Nagarajan ◽  
Stephen J. Brandt

Abstract The multifunctional LIM domain-binding protein Ldb1 is important in multiple developmental programs, including hematopoiesis. An evolutionarily conserved family of proteins with single-stranded DNA-binding activity, the SSBPs, has been shown to act as Ldb1 partners and augment its biological actions. We recently established that Ssbp2 and Ssbp3 were components of an E-box-GATA DNA-binding complex in murine erythroid progenitors containing the LIM-only protein Lmo2 and transcription factors Tal1, E2A, and Gata1 and showed these SSBPs stimulated E box-GATA DNA-binding activity and inhibited Ldb1 ubiquitination and subsequent proteasomal degradation (Genes & Dev.21:942–955, 2007). As its SSBP interaction domain (Ldb1/Chip conserved domain or LCCD) is adjacent to Ldb1’s N-terminal dimerization domain (DD), we sought to determine whether SSBP binding affected Ldb1 dimerization. To investigate, the Ldb1 coding region was fused to the DNA-binding domain of the yeast transcription factor GAL4 (GAL4DBD) and in a second construct to the activation domain of herpesvirus VP16 (VP16AD). These fusion proteins were then expressed in mammalian cells with a luciferase reporter linked to a promoter with iterated GAL4 binding sites. Luciferase activity became detectable with coexpression of the VP16AD-Ldb1 and GAL4DBD-Ldb1 fusions, presumably from Ldb1 dimerization, which increased markedly with simultaneous expression of SSBP2. In contrast, SSBP2 (ΔLUFS) and Ldb1 (ΔLCCD) mutants incapable of interacting with Ldb1 and SSBPs, respectively, were inactive, suggesting that SSBP2 augmentation of Ldb1 dimerization involved direct protein-protein interactions. To exclude an effect of SSBP2 on turnover of Ldb1 fusion proteins, radiolabeled full-length Ldb1 and SSBP3 were prepared by in vitro transcription/translation, mixed, and subjected to chemical crosslinking. Addition of the crosslinker bis(sulfosuccinimidyl)-suberate (BS3) to Ldb1, but not SSBP3, led to the appearance of a radiolabeled protein with mobility in denaturing polyacrylamide gels approximately twice that of Ldb1, consistent with an Ldb1 homodimer. When SSBP3 and Ldb1 were mixed together and crosslinked, a dose-related increase was noted in a more retarded species predicted to contain two molecules each of Ldb1 and SSBP3, together with a decrease in monomeric Ldb1. Finally, two well-characterized dimerization-defective Ldb1 mutants, Ldb1(200–375) and Ldb1(50–375), failed to support the formation of the higher molecular weight species or to homodimerize. Thus, the SSBPs promoted assembly of ternary complexes incorporating both SSBP and Ldb1 in a manner dependent on Ldb1 dimerization. The failure to observe Ldb1-SSBP heterodimers in cross-linking experiments suggests, further, that the SSBPs interacted with preformed Ldb1 dimers. In summary, either through an allosteric effect on Ldb1’s DD or by altering the equilibrium between monomeric and dimeric species, the SSBPs promote Ldb1 oligomerization. Together with inhibition of Ldb1 ubiquitination and turnover, this would serve to augment Ldb1 function.


2001 ◽  
Vol 75 (6) ◽  
pp. 2839-2847 ◽  
Author(s):  
Chunxiao Wu ◽  
Rupa Roy ◽  
Daniel T. Simmons

ABSTRACT We have previously mapped the single-stranded DNA binding domain of large T antigen to amino acid residues 259 to 627. By using internal deletion mutants, we show that this domain most likely begins after residue 301 and that the region between residues 501 and 550 is not required. To study the function of this binding activity, a series of single-point substitutions were introduced in this domain, and the mutants were tested for their ability to support simian virus 40 (SV40) replication and to bind to single-stranded DNA. Two replication-defective mutants (429DA and 460EA) were grossly impaired in single-stranded DNA binding. These two mutants were further tested for other biochemical activities needed for viral DNA replication. They bound to origin DNA and formed double hexamers in the presence of ATP. Their ability to unwind origin DNA and a helicase substrate was severely reduced, although they still had ATPase activity. These results suggest that the single-stranded DNA binding activity is involved in DNA unwinding. The two mutants were also very defective in structural distortion of origin DNA, making it likely that single-stranded DNA binding is also required for this process. These data show that single-stranded DNA binding is needed for at least two steps during SV40 DNA replication.


Cell Research ◽  
2013 ◽  
Vol 23 (10) ◽  
pp. 1215-1228 ◽  
Author(s):  
Yucai Wang ◽  
Xiao Han ◽  
Fangming Wu ◽  
Justin W Leung ◽  
Megan G Lowery ◽  
...  

1983 ◽  
Vol 3 (7) ◽  
pp. 667-674 ◽  
Author(s):  
Urs Kuhnlein ◽  
Siu Sing Tsang ◽  
Opal Lokken ◽  
Silvian Tong ◽  
Daniel Twa

Human fibroblasts and HeLa cells contain two major DNA-binding activities for superhelical DNA, which can be separated by phosphocellulose chromatography. The DNA-binding activity which elutes first from the column coelutes with and is probably identical to a single-stranded-DNA-binding activity. The second activity has been characterized previously. It binds preferentially to super-helical DNA containing DNA damage, but does not bind to single-stranded DNA. Five cell lines derived from patients with the repairdeficiency syndrome xeroderma pigmentosum (XP) were analyzed for the presence of these binding activities. Four of the cell lines were from the A-complementation group and one was from the D-complementation group of XP. The binding activity with preference for damaged DNA was present in all cell lines. The single-stranded-DNA-binding activity was present in the XP-D cell line but was absent or reduced in all of the four XP-A cell lines tested.


1995 ◽  
Vol 15 (5) ◽  
pp. 2429-2436 ◽  
Author(s):  
S Sun ◽  
E S Stoflet ◽  
J G Cogan ◽  
A R Strauch ◽  
M J Getz

Transcriptional activation and repression of the vascular smooth muscle (VSM) alpha-actin gene in myoblasts and fibroblasts is mediated, in part, by positive and negative elements contained within an approximately 30-bp polypurine-polypyrimidine tract. This region contains binding sites for an essential transcription-activating protein, identified as transcriptional enhancer factor I (TEF-1), and two tissue-restrictive, sequence-specific, single-stranded-DNA-binding activities termed VACssBF1 and VACssBF2. TEF-1 has no detectable single-stranded-DNA-binding activity, while VACssBF1 and VACssBF2 have little, if any, affinity for double-stranded DNA. Site-specific mutagenesis experiments demonstrate that the determinants of VACssBF1 and VACssBF2 binding lie on opposite strands of the DNA helix and include the TEF-1 recognition sequence. Functional analysis of this region reveals that the CCAAT box-binding protein nuclear factor Y (NF-Y) can substitute for TEF-1 in activating VSM alpha-actin transcription but that the TEF-1-binding site is essential for the maintenance of full transcriptional repression. Importantly, replacement of the TEF-1-binding site with that for NF-Y diminishes the ability of VACssBF1 and VACssBF2 to bind to separated single strands. Additional activating mutations have been identified which lie outside of the TEF-1-binding site but which also impair single-stranded-DNA-binding activity. These data support a model in which VACssBF1 and VACssBF2 function as repressors of VSM alpha-actin transcription by stabilizing a local single-stranded-DNA conformation, thus precluding double-stranded-DNA binding by the essential transcriptional activator TEF-1.


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