Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Replication Protein A”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources

Functional characterization of replication protein A2 (RPA2) from Cryptosporidium parvum.

Replication protein A (RPA) is a heterotrimeric complex of single-stranded DNA-binding proteins that play multiple roles in eukaryotic DNA metabolism. The RPA complex is typically composed of heterologous proteins (termed RPA1, RPA2 and RPA3) in animals, plants and fungi, which possess different functions. Previously, two distinct, short-type RPA large subunits (CpRPA1 and CpRPA1B) from the apicomplexan parasite Cryptosporidium parvum were characterized. Here are reported the identification and characterization of a putative middle RPA subunit (CpRPA2) from this unicellular organism. Although the CpRPA2 gene encodes a predicted 40.1 kDa peptide, which is larger than other RPA2 subunits characterized to date, Western blot analysis of oocyst preparations detected a native CpRPA2 protein with a molecular mass of approximately 32 kDa, suggesting that CpRPA2 might undergo post-translational cleavage or the gene was translated at an alternative start codon. Immunofluorescence microscopy using a rabbit anti-CpRPA2 antibody revealed that CpRPA2 protein was mainly distributed in the cytosol (rather than the nuclei) of C. parvum sporozoites. Semi-quantitative RT-PCR data indicated that CpRPA2 was differentially expressed in a tissue culture model with highest expression in intracellular parasites infecting HCT-8 cells for 36 and 60 h. Sequence comparison suggests that RPA2 is a group of poorly conserved proteins. Nonetheless, functional analyses of recombinant proteins confirmed that CpRPA2 is a single-stranded DNA-binding protein and that it could serve as an in vitro phosphorylation target by a DNA-dependent protein kinase. The minimal length of poly(dT) required for CpRPA2 binding is 17 nucleotides, and the DNA-binding capability was inhibited by phosphorylation in vitro. These observations provide additional evidence on the divergence of RPA proteins between C. parvum and host, implying that the parasite DNA replication machinery could be explored as a chemotherapeutic target.

Amino Acid Sequence↗

Replication protein A: a heterotrimeric, single-stranded DNA-binding protein required for eukaryotic DNA metabolism.

Replication protein A [RPA; also known as replication factor A (RFA) and human single-stranded DNA-binding protein] is a single-stranded DNA-binding protein that is required for multiple processes in eukaryotic DNA metabolism, including DNA replication, DNA repair, and recombination. RPA homologues have been identified in all eukaryotic organisms examined and are all abundant heterotrimeric proteins composed of subunits of approximately 70, 30, and 14 kDa. Members of this family bind nonspecifically to single-stranded DNA and interact with and/or modify the activities of multiple proteins. In cells, RPA is phosphorylated by DNA-dependent protein kinase when RPA is bound to single-stranded DNA (during S phase and after DNA damage). Phosphorylation of RPA may play a role in coordinating DNA metabolism in the cell. RPA may also have a role in modulating gene expression.

DNA↗

The weak interdomain coupling observed in the 70 kDa subunit of human replication protein A is unaffected by ssDNA binding.

Replication protein A (RPA) is a heterotrimeric, multi-functional protein that binds single-stranded DNA (ssDNA) and is essential for eukaryotic DNA metabolism. Using heteronuclear NMR methods we have investigated the domain interactions and ssDNA binding of a fragment from the 70 kDa subunit of human RPA (hRPA70). This fragment contains an N-terminal domain (NTD), which is important for hRPA70-protein interactions, connected to a ssDNA-binding domain (SSB1) by a flexible linker (hRPA70(1-326)). Correlation analysis of the amide (1)H and (15)N chemical shifts was used to compare the structure of the NTD and SSB1 in hRPA70(1-326) with two smaller fragments that corresponded to the individual domains. High correlation coefficients verified that the NTD and SSB1 maintained their structures in hRPA70(1-326), indicating weak interdomain coupling. Weak interdomain coupling was also suggested by a comparison of the transverse relaxation rates for hRPA70(1-326) and one of the smaller hRPA70 fragments containing the NTD and the flexible linker (hRPA70(1-168)). We also examined the structure of hRPA70(1-326) after addition of three different ssDNA substrates. Each of these substrates induced specific amide (1)H and/or (15)N chemical shift changes in both the NTD and SSB1. The NTD and SSB1 have similar topologies, leading to the possibility that ssDNA binding induced the chemical shift changes observed for the NTD. To test this hypothesis we monitored the amide (1)H and (15)N chemical shift changes of hRPA70(1-168) after addition of ssDNA. The same amide (1)H and (15)N chemical shift changes were observed for the NTD in hRPA70(1-168) and hRPA70(1-326). The NTD residues with the largest amide (1)H and/or (15)N chemical shift changes were localized to a basic cleft that is important for hRPA70-protein interactions. Based on this relationship, and other available data, we propose a model where binding between the NTD and ssDNA interferes with hRPA70-protein interactions.

Amides↗

Membrane-bound tomato mosaic virus replication proteins participate in RNA synthesis and are associated with host proteins in a pattern distinct from those that are not membrane bound.

Extracts of vacuole-depleted, tomato mosaic virus (ToMV)-infected plant protoplasts contained an RNA-dependent RNA polymerase (RdRp) that utilized an endogenous template to synthesize ToMV-related positive-strand RNAs in a pattern similar to that observed in vivo. Despite the fact that only minor fractions of the ToMV 130- and 180-kDa replication proteins were associated with membranes, the RdRp activity was exclusively associated with membranes. A genome-sized, negative-strand RNA template was associated with membranes and was resistant to micrococcal nuclease unless treated with detergents. Non-membrane-bound replication proteins did not exhibit RdRp activity, even in the presence of ToMV RNA. While the non-membrane-bound replication proteins remained soluble after treatment with Triton X-100, the same treatment made the membrane-bound replication proteins in a form that precipitated upon low-speed centrifugation. On the other hand, the detergent lysophosphatidylcholine (LPC) efficiently solubilized the membrane-bound replication proteins. Upon LPC treatment, the endogenous template-dependent RdRp activity was reduced and exogenous ToMV RNA template-dependent RdRp activity appeared instead. This activity, as well as the viral 130-kDa protein and the host proteins Hsp70, eukaryotic translation elongation factor 1A (eEF1A), TOM1, and TOM2A copurified with FLAG-tagged viral 180-kDa protein from LPC-solubilized membranes. In contrast, Hsp70 and only small amounts of the 130-kDa protein and eEF1A copurified with FLAG-tagged non-membrane-bound 180-kDa protein. These results suggest that the viral replication proteins are associated with the intracellular membranes harboring TOM1 and TOM2A and that this association is important for RdRp activity. Self-association of the viral replication proteins and their association with other host proteins may also be important for RdRp activity.

Cell Membrane↗

The bacteriophage lambda DNA replication protein P inhibits the oriC DNA- and ATP-binding functions of the DNA replication initiator protein DnaA of Escherichia coli.

Under the condition of expression of lambda P protein at lethal level, the oriC DNA-binding activity is significantly affected in wild-type E. coli but not in the rpl mutant. In purified system, the lambda P protein inhibits the binding of both oriC DNA and ATP to the wild-type DnaA protein but not to the rpl DnaA protein. We conclude that the lambda P protein inhibits the binding of oriC DNA and ATP to the wild-type DnaA protein, which causes the inhibition of host DNA synthesis initiation that ultimately leads to bacterial death. A possible beneficial effect of this interaction of lambda P protein with E. coli DNA initiator protein DnaA for phage DNA replication has been proposed.

Adenosine Triphosphate↗

The majority of human replication protein A remains complexed throughout the cell cycle.

Replication Protein A (RPA), the replicative single-strand DNA binding protein from eukaryotic cells, is a stable heterotrimeric complex consisting of three polypeptides. Cytological studies have investigated the subcellular distribution and association characteristics of the three RPA subunits during different stages of the cell cycle with varying results. In this study, various HeLa cell fractions were subjected to separation by either immunoprecipitation or velocity sedimentation. These separations were evaluated by immunoblotting for specific RPA subunits to determine whether the RPA in these fractions retains its heterotrimeric association. Immunoprecipitation of either the large (RPA70) or middle-sized (RPA32) subunit of RPA followed by immunoblotting for the other subunits demonstrate that RPA remains complexed throughout the G(1), S and G(2) phases of the cell cycle. Immunoprecipitation and sedimentation separations of both the nucleosolic and chromatin-bound RPA populations from both cycling and nocodazole-blocked cells showed that the majority of RPA remains complexed under all conditions examined. Consistent with previous reports, hypotonic extracts from 293 cells were shown to contain some RPA32 not complexed with RPA70. These results indicate that in some cell types, extracts may contain small amounts of RPA32 free of RPA70; however, in HeLa cells the majority of RPA clearly remains complexed as a heterotrimer throughout the cell cycle.

Blotting, Western↗

Specific binding of tombusvirus replication protein p33 to an internal replication element in the viral RNA is essential for replication.

The mechanism of template selection for genome replication in plus-strand RNA viruses is poorly understood. Using the prototypical tombusvirus, Tomato bushy stunt virus (TBSV), we show that recombinant p33 replicase protein binds specifically to an internal replication element (IRE) located within the p92 RNA-dependent RNA polymerase coding region of the viral genome. Specific binding of p33 to the IRE in vitro depends on the presence of a C.C mismatch within a conserved RNA helix. Interestingly, the absence of the p33:p33/p92 interaction domain in p33 prevented specific but allowed nonspecific RNA binding, suggesting that a multimeric form of this protein is involved in the IRE-specific interaction. Further support for the selectivity of p33 binding in vitro was provided by the inability of the replicase proteins of the closely related Turnip crinkle virus and distantly related Hepatitis C virus to specifically recognize the TBSV IRE. Importantly, there was also a strong correlation between p33:IRE complex formation in vitro and viral replication in vivo, where mutations in the IRE that disrupted selective p33 binding in vitro also abolished TBSV RNA replication both in plant and in Saccharomyces cerevisiae cells. Based on these findings and the other known properties of p33 and the IRE, it is proposed that the p33:IRE interaction provides a mechanism to selectively recruit viral RNAs into cognate viral replicase complexes. Since all genera in Tombusviridae encode comparable replicase proteins, these results may be relevant to other members of this large virus family.

Binding Sites↗

Specific binding of a cellular DNA replication protein to the origin of replication of adenovirus DNA.

Nuclear factor I, a 47-kilodalton protein, purified from nuclear extracts of uninfected HeLa cells, is involved in the initiation and possibly the elongation of replicating adenovirus (Ad) DNA in vitro. The binding of nuclear factor I to DNA has been monitored by a filter binding assay of nuclear factor I to DNA has been monitored by a filter binding assay using plasmid pLA1 DNA, which contains a 3,290 base-pair fragment derived from the left-hand terminus (coordinates, 0-9.4 map units) of Ad serotype 5 DNA. Nuclear factor I binds selectively to a double-stranded fragment spanning nucleotides 0-451 to the Ad genome. The retention of the 451-base-pair DNA fragment-nuclear factor I complex on nitrocellulose filters does not require Mg2+ or ATP and is resistant to high ionic strength. DNase I protection experiments revealed that nuclear factor I binds to a nucleotide sequence located at position 17-48, close to the terminus of Ad DNA. This 32-nucleotide sequence contains four "consensus" sequences present in various serotypes of Ad DNA and is capable of forming higher ordered structures. The role of nuclear factor I and this DNA sequence in the generation of Ad preterminal protein-dCMP initiation complex is discussed.

Adenoviridae↗

Cryptosporidium parvum possesses a short-type replication protein A large subunit that differs from its host.

Replication protein A (RPA) consisting of three subunits is a eukaryotic single-stranded DNA (ssDNA)-binding protein involved in DNA replication, repair and recombination. We report here the identification and characterization of a RPA large subunit (CpRPA1) gene from the apicomplexan Cryptosporidium parvum. The CpRPA1 gene encodes a 53.9-kDa peptide that is remarkably smaller than that from other eukaryotes (i.e. approximately 70 kDa) and is actively expressed in both free sporozoites and parasite intracellular stages. This short-type RPA large subunit has also been characterized from one other protist, Crithidia fasciculata. Three distinct domains have been identified in the RPA large subunit of humans and yeasts: an N-terminal protein interaction domain, a central ssDNA-binding area, and a C-terminal subunit-interacting region. Sequence analysis reveals that the short-type RPA large subunit differs from that of other eukaryotes in that only the domains required for ssDNA binding and heterotrimer formation are present. It lacks the N-terminal domain necessary for the binding of proteins mainly involved in DNA repair and recombination. This major structural difference suggests that the mechanism for DNA repair and recombination in some protists differs from that of other eukaryotes. Since replication proteins play an essential role in the cell cycle, the fact that RPA proteins of C. parvum differ from those of its host suggests that RPA be explored as a potential chemotherapeutic target for controlling cryptosporidiosis and/or diseases caused by other apicomplexans.

Amino Acid Sequence↗

Mechanism underlying replication protein a stimulation of DNA ligase I.

Replication protein A (RPA) is a heterotrimeric single-stranded DNA-binding protein that participates in multiple DNA transactions that include replication and repair. Base excision repair is a central DNA repair pathway, responsible for the removal of damaged bases. We have shown previously that RPA was able to stimulate long patch base excision repair reconstituted in vitro. Herein we show that human RPA stimulates the activity of the base excision repair component human DNA ligase I by approximately 15-fold. Other analyzed single-stranded binding proteins would not substitute, attesting to the specificity of the stimulation. Conversely, RPA was unable to stimulate the functionally homologous ATP-dependent ligase from T4 bacteriophage. Kinetic analyses suggest that catalysis of ligation is enhanced by RPA, as a 4-fold increase in k(cat) is observed, whereas K(m) is not significantly changed. Substrate competition experiments further support the conclusion that RPA does not alter the specificity or rate of substrate binding by DNA ligase I. Additionally, RPA is unable to significantly enhance ligation on substrates containing an unannealed 3'-upstream primer terminus, suggesting that RPA does not stabilize the nick site to enhance ligase recognition. Furthermore when DNA ligase I is pre-bound to the substrate and limited to a single turnover, RPA is still able to stimulate ligation. Overall, the results support a mechanism of stimulation that involves increasing the rate of catalysis of ligation.

Bacteriophage T4↗

The RPA32 subunit of human replication protein A contains a single-stranded DNA-binding domain.

Replication protein A (RPA) is a conserved nuclear single-stranded DNA (ssDNA)-binding protein. Human RPA (hRPA) comprises three subunits of approximately 70, 32, and 14 kDa (hRPA70, hRPA32 and hRPA14). RPA is known to bind ssDNA through two ssDNA-binding domains in the RPA70 subunit. Here, we demonstrate that the complex of hRPA32 and hRPA14 has an ssDNA-binding domain. Limited proteolysis of the hRPA14.32 complex defined a core dimer composed of the central region of hRPA32 (amino acids 43-171) and RPA14. The core dimer bound ssDNA with an affinity of approximately 10-50 microM, which is at least 100-fold more avid than the DNA-binding affinity of the intact dimer. Analysis of the predicted secondary structure of hRPA32 suggests that amino acids 63-150 of hRPA32 form an ssDNA-binding domain similar in structure to each of those in hRPA70. The complex of hRPA14 and hRPA32-(43-171) in turn formed a trimeric complex with the C-terminal region of hRPA70 (amino acids 436-616). The ssDNA-binding affinity of this trimeric complex was 3 to 5-fold higher than hRPA14.32-(43-171) alone, suggesting a role for the C terminus of hRPA70 in ssDNA binding.

Amino Acid Sequence↗

Targeting the E1 replication protein to the papillomavirus origin of replication by complex formation with the E2 transactivator.

The mechanism by which transcription factors stimulate DNA replication in eukaryotes is unknown. Bovine papillomavirus DNA synthesis requires the products of the viral E1 gene and the transcriptional activator protein encoded by the E2 gene. Experimental data showed that the 68-kilodalton (kD) E1 protein formed a complex with the 48-kD E2 transcription factor. This complex bound specifically to the viral origin of replication, which contains multiple binding sites for E2. Repressor proteins encoded by the E2 open reading frame failed to complex with E1 suggesting that the 162-amino acid region of E2 that participates in transactivation contained critical determinants for interaction with E1. The physical association between a replication protein and a transcription factor suggests that transcriptional activator proteins may function in targeting replication initiator proteins to their respective origins of replication.

Animals↗

Protein n, a primosomal DNA replication protein of Escherichia coli. Purification and characterization.

Protein n, essential in forming the primosome for the in vitro conversion of phi X174 single-stranded (SS) DNA to the duplex replicative form (RF), has been purified about 5000-fold to near homogeneity from Escherichia coli. Protein n is heat- and acid-resistant and N-ethyl-maleimide-sensitive. It appears to be a dimer of 12,000 (+/- 2000)-dalton polypeptides. About 80 molecules of protein n are present/cell. Protein n binding to phi X SS DNA depends on the presence of single-strand binding protein (SSB). This requirement for SSB reflects a direct interaction of protein n and SSB. About 30 protein n monomers can be bound to an SSB-coated circle. However, in forming the primosome on an SSB-coated phi X circle, an input of only 2-3 protein n monomers is required and 1 monomer bound/circle. Retention of this low level of protein n on SSB-coated phi X SS DNA is dependent upon protein n', a DNA-dependent ATPase (dATPase) that guides primosome assembly. This single protein n monomer is retained in the assembled primosome, which is conserved on the completed parental RF and participates in the next stage of the replicative cycle, production of progeny RF.

Amino Acids↗

In vivo and in vitro studies of a copy number mutation of the RepA replication protein of plasmid pSC101.

The RepA replication protein of plasmid pSC101 binds as a monomer to three repeated sequences (RS1, RS2, and RS3) in the replication origin of the plasmid to initiate duplication and binds as a dimer to two inversely repeated sequences (IR1 and IR2) in its promoter region (D. Manen, L. C. Upegui-Gonzalez, and L. Caro, Proc. Natl. Acad. Sci. USA 89:8923-8927, 1992). The binding to IR2 autoregulates repA transcription (P. Linder, G. Churchward, G. X. Xia, Y. Y. Yu, and L. Caro, J. Mol. Biol. 181:383-393, 1985). A mutation in the protein RepA(cop) that affects a single amino acid increases the plasmid copy number fourfold. In vivo experiments show that, when provided in trans under a foreign promoter, the RepA(cop) protein increases the replication of a plasmid containing the origin of replication without repA, whereas it decreases the repression of its own promoter. In vitro experiments show that the purified RepA(cop) protein binds more efficiently to the repeated sequences within the origin than does RepA and that its binding to these sequences is more specific than that of RepA. Binding to an inversely repeated sequence within the repA promoter gives opposite results: the wild-type protein binds efficiently to that sequence, whereas the mutated protein binds less efficiently and less specifically. Footprint experiments confirmed these results and, in addition, showed a difference in the pattern of protection of the inversely repeated sequences by the mutant protein. Equilibrium binding experiments showed that the formation of protein-probe complexes at increasing concentrations of protein had a sigmoidal shape for binding to RS sequences and a hyperbolic shape for binding to IR sequences. The results, together with earlier work (G.-X. Xia, D. Manen, T. Goebel, P. Linder, G. Churchward, and L. Caro, Mol. Microbiol. 5:631-640, 1991), confirm that the binding of RepA to RS sequences plays a crucial role in the regulation of plasmid replication and that its binding to IR sequences plays a role in the autoregulation of RepA expression. They also demonstrate that the two separate functions of the protein are effected by two different forms of binding to the target sites.

Amino Acid Sequence↗

The structure and function of the HSV DNA replication proteins: defining novel antiviral targets.

The absolute dependence of herpes simplex virus (HSV) replication on HSV DNA polymerase and six other viral-encoded replication proteins implies that specific inhibitors of these proteins' functions would be potent antiviral agents. The only currently licensed anti-herpes simplex drug, acyclovir, is an inhibitor of HSV DNA polymerase and is widely held to block viral replication primarily by specifically inhibiting viral DNA replication. In spite of the substantial advance in HSV therapy in recent years through the introduction of acyclovir, this anti-HSV compound and most of the other compounds under pharmaceutical development are substrate analogs. Since antiviral drug resistance has become an issue of increasing clinical importance, the need for structurally unrelated agents which incorporate novel mechanisms of viral inhibition is apparent. Understanding the structure and function of herpesvirus DNA polymerase and its interaction with the other six essential replication proteins at the replication origin should assist us in designing the next generation of therapeutic agents. The sequences of these proteins have been deduced and the proteins themselves have been expressed and purified in a variety of systems. The current challenge, therefore, is to use the available information about these proteins to identify and develop new, exquisitely specific antiviral therapeutics. In this review, we have summarized the current approaches and the results of structure/function studies of the herpes virus proteins essential for DNA replication, with the goal of more precisely defining novel antiviral targets.

Amino Acid Sequence↗

Regulation of dna replication after heat shock by replication protein a-nucleolin interactions.

Heat shock inhibits replicative DNA synthesis, but the underlying mechanism remains unknown. We investigated mechanistic aspects of this regulation in melanoma cells using a simian virus 40 (SV40)-based in vitro DNA replication assay. Heat shock (44 degrees C) caused a monotonic inhibition of cellular DNA replication following exposures for 5-90 min. SV40 DNA replication activity in extracts of similarly heated cells also decreased after 5-30 min of exposure, but returned to near control levels after 60-90 min of exposure. This transient inhibition of SV40 DNA replication was eliminated by recombinant replication protein A (rRPA), suggesting a regulatory process targeting this key DNA replication factor. SV40 DNA replication inhibition was associated with a transient increase in the interaction between nucleolin and RPA that peaked at 20-30 min. Because binding to nucleolin compromises the ability of RPA to support SV40 DNA replication, we suggest that the observed interaction reflects a mechanism whereby DNA replication is regulated after heat shock. The relevance of this interaction to the regulation of cellular DNA replication is indicated by the transient translocation in heated cells of nucleolin from the nucleolus into the nucleoplasm with kinetics very similar to those of SV40 DNA replication inhibition and of RPA-nucleolin interaction. Because the targeting of RPA by nucleolin in heated cells occurs in an environment that preserves the activity of several essential DNA replication factors, active processes may contribute to DNA replication inhibition to a larger degree than presently thought. RPA-nucleolin interactions may reflect an early step in the regulation of DNA replication, as nucleolin relocalized into the nucleolus 1-2 h after heat exposure but cellular DNA replication remained inhibited for up to 8 h. We propose that the nucleolus functions as a heat sensor that uses nucleolin as a signaling molecule to initiate inhibitory responses equivalent to a checkpoint.

DNA Replication↗

Transcription of genes encoding DNA replication proteins is coincident with cell cycle control of DNA replication in Caulobacter crescentus.

DNA replication in the dimorphic bacterium Caulobacter crescentus is tightly linked to its developmental cell cycle. The initiation of chromosomal replication occurs concomitantly with the transition of the motile swarmer cell to the sessile stalked cell. To identify the signals responsible for the cell cycle control of DNA replication initiation, we have characterized a region of the C. crescentus chromosome containing genes that are all involved in DNA replication or recombination, including dnaN, recF, and gyrB. The essential dnaN gene encodes a homolog of the Escherichia coli beta subunit of DNA polymerase III. It is transcribed from three promoters; one is heat inducible, and the other two are induced at the transition from swarmer to stalked cell, coincident with the initiation of DNA replication. The single gyrB promoter is induced at the same time point in the cell cycle. These promoters, as well as those for several other genes encoding DNA replication proteins that are induced at the same time in the cell cycle, share two sequence motifs, suggesting that they represent a family whose transcription is coordinately regulated.

Amino Acid Sequence↗

The acidic transcriptional activation domains of VP16 and p53 bind the cellular replication protein A and stimulate in vitro BPV-1 DNA replication.

For papillomavirus DNA replication, the E2 enhancer protein cooperatively assists in binding of the E1 helicase to the origin. We report that, at limiting E1 and E2 levels, the enhancer proteins GAL4-VP16 and GAL4-p53(1-73) stimulate BPV in vitro DNA replication. This cell-free system was used to ascertain whether the acidic activation domains have a cellular target important for replication. Cellular extracts were depleted of replication activity by passage through a VP16 affinity column. The protein depleted was the cellular factor replication protein A. The direct interaction between replication protein A and VP16, as well as the activation of replication by VP16, is dependent upon the C-terminus of the VP16 activation domain. E2 and the activation domain of p53 also interact with replication protein A. We suggest that a link between transcription and replication involves factors that help convert a closed DNA complex to an open complex.

Adenovirus E2 Proteins↗