RPA2 Is a Direct Downstream Target for ATR to Regulate the S-phase Checkpoint

Olson, Erin; Nievera, Christian J.; Klimovich, V. Ya.; Fanning, Ellen; Wu, Xiaohua

doi:10.1074/jbc.m605121200

Cited by 172 publications

(203 citation statements)

References 68 publications

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“…For both modifications, the presence of DNA-PK CS did not have any notable effects on the Ser(P) 33 and Ser(P) 29 signals in the intermediate position. Combined with past studies examining RPA phosphorylation by DNA-PK (22,23), these data are consistent with the proposal that DNA-PK is a primary but not sole kinase competent to phosphorylate Thr 21 (24) in vivo, we believe that the reduction in Ser(P) 29 and Ser(P) 33 formation in cells lacking DNA-PK CS is a consequence of the RPA phosphorylation state affecting the phosphorylation of other RPA molecules in trans (see below).…”

Section: Signal (Lanes 3 and 4)supporting

confidence: 73%

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Sequential and Synergistic Modification of Human RPA Stimulates Chromosomal DNA Repair

Anantha

Vassin

Borowiec

2007

Journal of Biological Chemistry

146

211

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The activity of human replication protein A (RPA) in DNA replication and repair is regulated by phosphorylation of the middle RPA2 subunit. It has previously been shown that up to nine different N-terminal residues are modified in vivo and in response to genotoxic stress. Using a novel antibody against phospho-Ser 29 , a moiety formed by cyclin-Cdk, we observed that RPA2 was phosphorylated during mitosis in nonstressed cells. Robust phosphorylation of Ser 29 was also seen in interphase cells following treatment with the DNA-damaging agent camptothecin, a rare example of stress stimulating the modification of a repair factor by cyclin-Cdk. RPA2 phosphorylation is regulated both in cis and trans. Cis-phosphorylation follows a preferred pathway. (That is, the initial modification of Ser 33 by ATR stimulates subsequent phosphorylation of Cdk sites Ser 23 and Ser 29 ). These events then facilitate modification of Thr 21 and extreme N-terminal sites Ser 4 and Ser 8 , probably by DNA-PK. Our data also indicate that the phosphorylation of one RPA molecule can influence the phosphorylation of other RPA molecules in trans. Cells in which endogenous RPA2 was "replaced" with a double S23A/S29A-RPA2 mutant were seen to have an abnormal cell cycle distribution both in normal and in stressed cells. Such cells also showed aberrant DNA damage-dependent RPA foci and had persistent staining of ␥H2AX following DNA damage. Our data indicate that RPA phosphorylation facilitates chromosomal DNA repair. We postulate that the RPA phosphorylation pattern provides a means to regulate the DNA repair pathway utilized.Replication protein A (RPA) 2 is a heterotrimeric singlestranded DNA-binding factor that is critical for the "three Rs" of eukaryotic DNA enzymology: DNA replication, DNA recombination, and DNA repair (1, 2). For DNA replication, the study of cellular and viral model systems demonstrates that RPA is needed both for origin denaturation and replication elongation, in the latter case to facilitate the switch from DNA polymerase ␣ to DNA polymerase ␦ during Okazaki fragment synthesis (3). RPA acts in homologous recombination (HR) to stimulate DNA annealing using physical interactions with Rad52 (4 -7) and in HR-mediated DNA repair, probably employing specific interactions with BRCA2 (8, 9). RPA is a required factor in both the nucleotide excision (10, 11) and mismatch repair pathways (12, 13) and in somatic hypermutation (14). Because of these many roles, it is of significant interest to understand the mechanisms that regulate RPA activity.Of the ϳ70-kDa (RPA1), 30-kDa (RPA2), and 14-kDa (RPA3) subunits, human RPA is subject to extensive phosphorylation on RPA2 (2) and at one RPA1 site (15). The N-terminal 33 residues of RPA2 undergo both cell cycle-and stress-dependent phosphorylation on approximately nine sites (Fig. 1A), which are thought to exist in an unstructured conformation (16,17). Ser 23 and Ser 29 are constitutively modified during mitosis by cyclin B-Cdk1 (18, 19) and have been suggested to be partially modified beginni...

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Section: Signal (Lanes 3 and 4)supporting

confidence: 73%

“…RPA containing RPA2 mutations that mimic hyperphosphorylation selectively prevent the association of RPA with replication centers but not repair foci (24,27). Similarly, others have found that ATR-dependent phosphorylation of RPA inhibits DNA synthesis following UV irradiation (24).…”

mentioning

confidence: 99%

Sequential and Synergistic Modification of Human RPA Stimulates Chromosomal DNA Repair

Anantha

Vassin

Borowiec

2007

Journal of Biological Chemistry

146

211

View full text Add to dashboard Cite

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“…4B). ATR kinase initiates the signaling cascade in response to the collapse of stalled replication forks and promotes phosphorylation of RPA at Ser 33 (32,33).…”

Section: Resultsmentioning

confidence: 99%

Progerin-Induced Replication Stress Facilitates Premature Senescence in Hutchinson-Gilford Progeria Syndrome

Wheaton

Campuzano

et al. 2017

Molecular and Cellular Biology

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Hutchinson-Gilford progeria syndrome (HGPS) is caused by a mutation in LMNA that produces an aberrant lamin A protein, progerin. The accumulation of progerin in HGPS cells leads to an aberrant nuclear morphology, genetic instability, and p53-dependent premature senescence. How p53 is activated in response to progerin production is unknown. Here we show that young cycling HGPS fibroblasts exhibit chronic DNA damage, primarily in S phase, as well as delayed replication fork progression. We demonstrate that progerin binds to PCNA, altering its distribution away from replicating DNA in HGPS cells, leading to ␥H2AX formation, ATR activation, and RPA Ser33 phosphorylation. Unlike normal human cells that can be immortalized by enforced expression of telomerase alone, immortalization of HGPS cells requires telomerase expression and p53 repression. In addition, we show that the DNA damage response in HGPS cells does not originate from eroded telomeres. Together, these results establish that progerin interferes with the coordination of essential DNA replication factors, causing replication stress, and is the primary signal for p53 activation leading to premature senescence in HGPS. Furthermore, this damage response is shown to be independent of progerin farnesylation, implying that unprocessed lamin A alone causes replication stress.KEYWORDS HGPS, progerin, senescence, aging, p53, telomere T he study of children with rare accelerated aging (progeria) syndromes has provided insight into the normal process of aging. Hutchinson-Gilford progeria syndrome (HGPS) is caused by a heterozygous, autosomal dominant mutation in LMNA (1), the gene that encodes lamin A, a key structural protein in the nuclear lamina. The lamina, a protein network that lines the inner nuclear membrane, provides structural support for the nucleus and is important for chromatin attachment, DNA replication, nuclear organization, and gene transcription in ways that are not completely understood. Farnesylation of prelamin A at the C terminus allows targeting to the inner nuclear membrane, where it is subsequently cleaved by the zinc metalloproteinase Zmpste24 to release mature lamin A into the lamina and nucleoplasm. In HGPS, the most common LMNA mutation (G608G) activates a cryptic splice donor site in exon 11, resulting in prelamin A mRNA with a 150-bp internal deletion, leading to a 50-amino-acid truncation in a region that contains the Zmpste24 cleavage site (reviewed in reference 2). The mutant lamin, termed progerin, retains the farnesyl lipid anchor, interferes with the integrity of the nuclear lamina, and causes the formation of misshapen nuclei. The retention of progerin on the inner nuclear membrane interferes with the function and normal distribution of lamin A, causing a loss of peripheral heterochromatin, increased DNA damage, impaired recruitment of DNA repair proteins to sites of DNA damage (3), and persistent activation of DNA damage response proteins (4). In addition to its

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“…First, expression of an RPA2 subunit that mimics hyper-phosphorylation results in RPA having reduced loading onto DNA replication forks in vivo. 5,6 These data have led to the suggestion that phosphorylation causes a shift of RPA activity to favor DNA repair at the expense of DNA replication. Second, RPA2 phosphorylation in interphase cells stimulates repair of chromosomal DNA damage caused either by camptothecin or bleomycin treatment.…”

Section: Rpa Activity In Mitosismentioning

confidence: 99%